Yeah that's one of the things that bothers me,you don't actually get to be the bad guy and the way it looks corruption will be a really slow process,but once it's done rowan would longer care if Alexia sleeps around in fact he might encourage it in order to gain more power over the twins/in general.I'm still waiting for option to play evil Rowan.
There's a lot of ways for rowan to get corrupted quickly,trying to gain power in order to bridge the gap between him and the twins and there are a lot of ways to do this(I'm sure the writers could come up with better ones than me).
I think corrupting rowan should be a priority since it will give the players the option to actually play the bad guy and the NTR aspect people complain about will be less significant since rowan will sacrifice his wife's "purity" for knowledge/power. and it is the main feature of the game("You are the bad guy")