Editing the database does it affect long term playing of game?

Right now I know this is cheating but I'm a bit peeved how I signed neymar for villa in demo but on full game he's not interested. So my question is if I upped the reputation of villa in the database would this affect the playing of the game? E.g if I dominated all comps with the standard database villas reputation would increase would it still increase if I edited the database or would it stay the same as I edited it?

Anything you do in the pre-game editor stays throughout your save (and any later ones if you don't change it back), so yes, it would affect your game.

Why don't you just 'cheat' by editing Neymar to be at Villa at the start of the game (and deduct £X from your transfer budget)?