I've yet to try managing a WPL side to success in Football Manager.
Back in the CM days I used to manage Aberystwyth Town to glory, and found it just about possible to maintain a fairly cooul side providing I won the league and made it as far as the group stages of the Champions League. The major problem with the WPL though, was always the small amount of revenue you could generate. Even with stadium expansion to boost your ticket sales you struggled. Heck i was making more money from gate receipts at home than I'd get awarded for winning a Welsh Cup.