Good idea but I dont think it should increase/decrease stats.
Advantages;
Condition goes up.
Morale goes up.
Relations improve with team mates and favoured club goes up.
Disadvantages;
Fall outs between team mates.
Cost of going away.
Match fitness decreases (would anyway if not playing mathes).
And of course in England it would mean you where knocked out the cups to be able to go away.
Something else to think about maybe would be room mates, for away games aswell.
The game decides who rooms with who but you could request your new Brazilian signing rooms with another native who has been at the club a few seasons.
This could improve relations between the two and help the settling in time.
It could be in the players profile who the player rooms with.