Not for everybody's liking, but below is the contents of an EDT file to create a Dutch/Belgian league.
Right now I'm putting all the dutch fields in the database, but it is playable without the non league fields.
If you like the idea, enjoy!
#SWAP 9 premiersites Belgium <-> Holland
"SWAP_TEAMS" "AZ" "Beveren"
"SWAP_TEAMS" "Ajax" "Cercle Brugge"
"SWAP_TEAMS" "Feyenoord" "Charleroi"
"SWAP_TEAMS" "Vitesse" "FC Brussels"
"SWAP_TEAMS" "Heerenveen" "Germinal Beerschot"
"SWAP_TEAMS" "PSV" "La Louvière"
"SWAP_TEAMS" "RKC" "Lierse"
"SWAP_TEAMS" "Roda" "Moeskroen"
"SWAP_TEAMS" "Groningen" "SV Roeselare"
# Bottom nine dutch and belgium premier swap with belgium 2nd class
"SWAP_TEAMS" "Antwerp" "NAC"
"SWAP_TEAMS" "Bergen" "ADO"
"SWAP_TEAMS" "Deinze" "RBC"
"SWAP_TEAMS" "Dessel" "Willem II"
"SWAP_TEAMS" "Eupen" "Sparta"
"SWAP_TEAMS" "Geel" "Heracles"
"SWAP_TEAMS" "Hamme" "Utrecht"
"SWAP_TEAMS" "KBHZ" "Twente"
"SWAP_TEAMS" "KV Kortrijk" "NEC"
"SWAP_TEAMS" "KV Mechelen" "Beveren"
"SWAP_TEAMS" "KVSK" "Cercle Brugge"
"SWAP_TEAMS" "OH Leuven" "Charleroi"
"SWAP_TEAMS" "Oostende" "FC Brussels"
"SWAP_TEAMS" "Ronse" "Germinal Beerschot"
"SWAP_TEAMS" "Tubize" "La Louvière"
"SWAP_TEAMS" "Union" "Lierse"
"SWAP_TEAMS" "Virton" "Moeskroen"
"SWAP_TEAMS" "Waasland" "SV Roeselare"
# Swap 3rd class A with dutch eerste divisie and belgium 2nd class (9 teams each)
"SWAP_TEAMS" "Aalst" "VVV"
"SWAP_TEAMS" "Bornem" "Excelsior"
"SWAP_TEAMS" "Diegem" "Volendam"
"SWAP_TEAMS" "FCV Dender" "Emmen"
"SWAP_TEAMS" "Kapellen" "Zwolle"
"SWAP_TEAMS" "Nieuwkerken" "Den Bosch"
"SWAP_TEAMS" "RC Mechelen" "Helmond"
"SWAP_TEAMS" "RC Waregem" "MVV"
"SWAP_TEAMS" "Rupel Boom" "Oostende"
"SWAP_TEAMS" "SK Maldegem" "Tubize"
"SWAP_TEAMS" "SW Harelbeke" "Ronse"
"SWAP_TEAMS" "Torhout" "Virton"
"SWAP_TEAMS" "Turnhout" "Antwerp"
"SWAP_TEAMS" "WS Woluwé" "Hamme"
"SWAP_TEAMS" "Wetteren" "KBHZ"
"SWAP_TEAMS" "Willebroek" "Union"
# Swap 3rd class A with dutch eerste divisie and belgium 2nd class (9 teams each)
"SWAP_TEAMS" "Bocholt" "Dessel"
"SWAP_TEAMS" "Couillet" "KV Kortrijk"
"SWAP_TEAMS" "Doornik" "OH Leuven"
"SWAP_TEAMS" "Francs Borains" "Eupen"
"SWAP_TEAMS" "Kelmis" "KV Mechelen"
"SWAP_TEAMS" "Kermt-Hasselt" "Bergen"
"SWAP_TEAMS" "Leopoldsburg" "KVSK"
"SWAP_TEAMS" "Montegnée" "Waasland"
"SWAP_TEAMS" "Olympic Charleroi" "TOP"
"SWAP_TEAMS" "Sprimont" "Telstar"
"SWAP_TEAMS" "Tienen" "Veendam"
"SWAP_TEAMS" "Tongeren" "Go Ahead"
"SWAP_TEAMS" "UR Namen" "Graafschap"
"SWAP_TEAMS" "Verviers" "AGOVV"
"SWAP_TEAMS" "Visé" "Cambuur"
"SWAP_TEAMS" "Walhain" "Dordrecht"
# Swap 4th class with belgium and dutch teams
# 4A
"SWAP_TEAMS" "Aalter" "Aalst"
"SWAP_TEAMS" "Diksmuide" "Bornem"
"SWAP_TEAMS" "Eine" "Diegem"
"SWAP_TEAMS" "Evergem" "FCV Dender"
"SWAP_TEAMS" "Lovendegem" "Kapellen"
"SWAP_TEAMS" "Oostnieuwkerke" "Nieuwkerken"
"SWAP_TEAMS" "Oudenaarde" "RC Mechelen"
"SWAP_TEAMS" "Péruwelz" "RC Waregem"
"SWAP_TEAMS" "RC Gent" "Fortuna"
"SWAP_TEAMS" "Rumbeke" "Lisse"
"SWAP_TEAMS" "US Centre" "DOTO"
"SWAP_TEAMS" "VG Oostende" "Rijnsburgse Boys"
"SWAP_TEAMS" "WS Lauwe" "Noordwijk"
"SWAP_TEAMS" "Wevelgem" "Katwijk"
"SWAP_TEAMS" "Winkel Sport" "IJsselmeervogels"
"SWAP_TEAMS" "Zottegem" "ASWH"
# 4B
"SWAP_TEAMS" "Berchem" "Deinze"
"SWAP_TEAMS" "Dilbeek" "Olympic Charleroi"
"SWAP_TEAMS" "Grimbergen" "Tienen"
"SWAP_TEAMS" "Kampenhout" "Tongeren"
"SWAP_TEAMS" "Kontich" "UR Namen"
"SWAP_TEAMS" "Lebeke-Aalst" "Verviers"
"SWAP_TEAMS" "Londerzeel" "Visé"
"SWAP_TEAMS" "Meldert" "Walhain"
"SWAP_TEAMS" "Opstal" "Haarlem"
"SWAP_TEAMS" "Opwijk" "SHO"
"SWAP_TEAMS" "RC Lebbeke" "SV Geinoord"
"SWAP_TEAMS" "Rhode-Verrewinkel" "O.N.S."
"SWAP_TEAMS" "Schoten" "SC Genemuiden"
"SWAP_TEAMS" "Temse" "Harkemase Boys"
"SWAP_TEAMS" "Uccle Léo" "DOS Kampen"
"SWAP_TEAMS" "Wilrijk" "Be Quick´28"
# 4C
"SWAP_TEAMS" "Aarschot" "Geel"
"SWAP_TEAMS" "Berkenbos" "Rupel Boom"
"SWAP_TEAMS" "Bree" "SW Harelbeke"
"SWAP_TEAMS" "Hedera Millen" "Torhout"
"SWAP_TEAMS" "Heist" "Turnhout"
"SWAP_TEAMS" "Hoogstraten" "WS Woluwé"
"SWAP_TEAMS" "Lichtaart" "Wetteren"
"SWAP_TEAMS" "Lyra" "Willebroek"
"SWAP_TEAMS" "Meerhout" "Eindhoven"
"SWAP_TEAMS" "Olen" "Achilles'29"
"SWAP_TEAMS" "Patro Eisden" "Be Quick 1887"
"SWAP_TEAMS" "RC Mol-Wezel" "HSC'21"
"SWAP_TEAMS" "Spouwen" "De Treffers/KEGRO"
"SWAP_TEAMS" "Thes Sport" "Rohda"
"SWAP_TEAMS" "Veldwezelt" "Schijndel"
"SWAP_TEAMS" "Zwarte Leeuw" "Gemert"
# 4D
"SWAP_TEAMS" "Aarlen" "Bocholt"
"SWAP_TEAMS" "Andenne" "Couillet"
"SWAP_TEAMS" "Bas-Oha" "Doornik"
"SWAP_TEAMS" "Bertrix" "Francs Borains"
"SWAP_TEAMS" "Bleid" "Kelmis"
"SWAP_TEAMS" "Ciney" "Kermt-Hasselt"
"SWAP_TEAMS" "Couvin-Mariembourg" "Leopoldsburg"
"SWAP_TEAMS" "FC Luik" "Montegnée"
"SWAP_TEAMS" "Hamoir" "Omniworld"
"SWAP_TEAMS" "Hannut" "De Baronie"
"SWAP_TEAMS" "Heppignies" "EVV"
"SWAP_TEAMS" "Hoei" "Argon"
"SWAP_TEAMS" "Malmédy" "Türkiyemspor"
"SWAP_TEAMS" "Seraing RUL" "Elinkwijk"
"SWAP_TEAMS" "Spa" "AFC"
"SWAP_TEAMS" "Spy" "ADO´20"
# swap non league teams
"SWAP_TEAMS" "989" "8150979"
"SWAP_TEAMS" "995" "8150942"
"SWAP_TEAMS" "996" "8159727"
"SWAP_TEAMS" "999" "8152546"
"SWAP_TEAMS" "1019" "8182085"
"SWAP_TEAMS" "1023" "527942"
"SWAP_TEAMS" "1027" "8158392"
"SWAP_TEAMS" "1029" "8179150"
"SWAP_TEAMS" "1030" "536246"
"SWAP_TEAMS" "1034" "8179267"
"SWAP_TEAMS" "1035" "8151593"
"SWAP_TEAMS" "1038" "539880"
"SWAP_TEAMS" "1041" "8176292"
"SWAP_TEAMS" "2317" "8160781"
"SWAP_TEAMS" "2318" "8158843"
"SWAP_TEAMS" "2319" "3200572"
"SWAP_TEAMS" "2321" "3200596"
"SWAP_TEAMS" "2324" "8150292"
"SWAP_TEAMS" "2325" "8154755"
"SWAP_TEAMS" "2326" "8158287"
"SWAP_TEAMS" "2328" "285"
"SWAP_TEAMS" "2331" "539807"
"SWAP_TEAMS" "2333" "8154752"
"SWAP_TEAMS" "2334" "8151596"
"SWAP_TEAMS" "2335" "8161397"
"SWAP_TEAMS" "2336" "8179414"
"SWAP_TEAMS" "2337" "8152841"
"SWAP_TEAMS" "2338" "197"
"SWAP_TEAMS" "2340" "532178"
"SWAP_TEAMS" "2341" "8158210"
"SWAP_TEAMS" "2342" "3200593"
"SWAP_TEAMS" "2343" "8176694"
"SWAP_TEAMS" "2345" "8151619"
"SWAP_TEAMS" "2346" "539404"
"SWAP_TEAMS" "2347" "536208"
"SWAP_TEAMS" "2348" "8154757"
"SWAP_TEAMS" "2349" "8177192"
"SWAP_TEAMS" "2350" "8150284"
"SWAP_TEAMS" "2352" "198"
"SWAP_TEAMS" "2353" "8154761"
"SWAP_TEAMS" "2354" "8160012"
"SWAP_TEAMS" "2355" "8436743"
"SWAP_TEAMS" "2356" "8154477"
"SWAP_TEAMS" "2357" "8153670"
"SWAP_TEAMS" "2358" "8154727"
"SWAP_TEAMS" "2359" "8150346"
"SWAP_TEAMS" "2361" "8436745"
"SWAP_TEAMS" "2362" "8154718"
"SWAP_TEAMS" "2364" "8177203"
"SWAP_TEAMS" "2366" "6600087"
"SWAP_TEAMS" "2367" "8180557"
"SWAP_TEAMS" "2369" "8154753"
"SWAP_TEAMS" "2370" "527961"
"SWAP_TEAMS" "2371" "8179174"
"SWAP_TEAMS" "2372" "8176739"
"SWAP_TEAMS" "2373" "8151518"
"SWAP_TEAMS" "2374" "8154764"
"SWAP_TEAMS" "2375" "8151564"
"SWAP_TEAMS" "2376" "8151485"
"SWAP_TEAMS" "2378" "8151855"
"SWAP_TEAMS" "2379" "8158158"
"SWAP_TEAMS" "2380" "8151826"
"SWAP_TEAMS" "2381" "532181"
"SWAP_TEAMS" "2382" "8181545"
"SWAP_TEAMS" "100729" "8150911"
"SWAP_TEAMS" "100881" "8150348"
"SWAP_TEAMS" "100883" "185"
"SWAP_TEAMS" "100885" "8154748"
"SWAP_TEAMS" "100893" "8154763"
"SWAP_TEAMS" "100896" "8153245"
"SWAP_TEAMS" "100904" "8158253"
"SWAP_TEAMS" "100909" "539841"
"SWAP_TEAMS" "100911" "8154117"
"SWAP_TEAMS" "100912" "8177231"
"SWAP_TEAMS" "100913" "8161611"
"SWAP_TEAMS" "100914" "8160803"
"SWAP_TEAMS" "100915" "8153301"
"SWAP_TEAMS" "100916" "8157703"
"SWAP_TEAMS" "100918" "8158295"
"SWAP_TEAMS" "100921" "187"
"SWAP_TEAMS" "100922" "8152383"
"SWAP_TEAMS" "100931" "230"
"SWAP_TEAMS" "100933" "8151009"
"SWAP_TEAMS" "100940" "291"
"SWAP_TEAMS" "100952" "8154805"
"SWAP_TEAMS" "100987" "8156468"
"SWAP_TEAMS" "100988" "8436735"
"SWAP_TEAMS" "101000" "8188125"
"SWAP_TEAMS" "101012" "200"
"SWAP_TEAMS" "101016" "8174660"
"SWAP_TEAMS" "101017" "8154241"
"SWAP_TEAMS" "101018" "190"
"SWAP_TEAMS" "101020" "8152328"
"SWAP_TEAMS" "101026" "192"
"SWAP_TEAMS" "101045" "193"
"SWAP_TEAMS" "101058" "8161703"
"SWAP_TEAMS" "102885" "8158300"
"SWAP_TEAMS" "102886" "8181595"
"SWAP_TEAMS" "102887" "8151947"
"SWAP_TEAMS" "115257" "8169489"
"SWAP_TEAMS" "851544" "8154229"
"SWAP_TEAMS" "851545" "8176685"
"SWAP_TEAMS" "851546" "8179274"
"SWAP_TEAMS" "851547" "6600092"
"SWAP_TEAMS" "851548" "536143"
"SWAP_TEAMS" "851549" "8182005"
"SWAP_TEAMS" "851550" "8152849"
"SWAP_TEAMS" "851553" "8160753"
"SWAP_TEAMS" "851672" "8150350"
"SWAP_TEAMS" "851673" "8170034"
"SWAP_TEAMS" "851675" "8158382"
"SWAP_TEAMS" "851676" "8182630"
"SWAP_TEAMS" "851677" "539868"
"SWAP_TEAMS" "851678" "8152821"
"SWAP_TEAMS" "851679" "8157203"
"SWAP_TEAMS" "851681" "210"
"SWAP_TEAMS" "851683" "8158147"
"SWAP_TEAMS" "851684" "201"
"SWAP_TEAMS" "851685" "8158218"
"SWAP_TEAMS" "851686" "8154725"
"SWAP_TEAMS" "851687" "8150990"
"SWAP_TEAMS" "851688" "8162620"
"SWAP_TEAMS" "852177" "8161714"
"SWAP_TEAMS" "854087" "8155035"
"SWAP_TEAMS" "855757" "8151525"
"SWAP_TEAMS" "855759" "8161596"
"SWAP_TEAMS" "856119" "8158204"
"SWAP_TEAMS" "856121" "8161518"
"SWAP_TEAMS" "856173" "539715"
"SWAP_TEAMS" "856457" "217"
"SWAP_TEAMS" "856539" "8165505"
"SWAP_TEAMS" "856949" "533424"
"SWAP_TEAMS" "857222" "8179391"
"SWAP_TEAMS" "857223" "8160295"
"SWAP_TEAMS" "857231" "8150969"
"SWAP_TEAMS" "857721" "8150286"
"SWAP_TEAMS" "858010" "8154765"
"SWAP_TEAMS" "858773" "8158142"
"SWAP_TEAMS" "859087" "8176020"
"SWAP_TEAMS" "859117" "8160411"
"SWAP_TEAMS" "859733" "8151560"
"SWAP_TEAMS" "859764" "539847"
"SWAP_TEAMS" "859830" "8169539"
"SWAP_TEAMS" "859852" "8158053"
"SWAP_TEAMS" "860024" "8158837"
"SWAP_TEAMS" "861618" "8154740"
"SWAP_TEAMS" "861650" "8158358"
"SWAP_TEAMS" "862076" "8154724"
"SWAP_TEAMS" "862435" "277"
"SWAP_TEAMS" "862437" "8158829"
"SWAP_TEAMS" "862775" "8152736"
"SWAP_TEAMS" "862778" "8152330"
"SWAP_TEAMS" "862779" "8151558"
"SWAP_TEAMS" "862781" "221"
"SWAP_TEAMS" "862782" "8151530"
"SWAP_TEAMS" "862785" "222"
"SWAP_TEAMS" "862788" "536331"
"SWAP_TEAMS" "862789" "8152876"
"SWAP_TEAMS" "863176" "8156373"
"SWAP_TEAMS" "3700360" "8436742"
"SWAP_TEAMS" "7200000" "8151936"
"SWAP_TEAMS" "8160177" "6600096"
"SWAP_TEAMS" "8161092" "8158274"
"SWAP_TEAMS" "8161661" "8169488"
"SWAP_TEAMS" "8177669" "8162622"
"SWAP_TEAMS" "8182255" "8150884"
Combined belgian and dutch league 
Linear Mode
