Eric not banging anyone BUT Ann and that being avoidable? Sure. But Eric banging Ann is pretty much intrinsic to Big Brother story wise. The entire concept of the game is that Ann who is dangerously submissive gets a new boyfriend. He insinuates himself into the family and the player has to stop them. If Eric ISN'T banging Ann, then what is he doing staying over at the house? Once they start dating they will be having sex, and if they aren't a lot of the subsequent story doesn't make a whole lot of sense. Ok, it never made much sense in the first place, but you can see my point. If you want a BB where Eric never existed, then Glamour exists, or a million other mods.
I am all for NTR content being avoidable, it should be when it makes sense. But in BB, assuming there is an attempt to make the game something that follows the plot of the original while expanding on it... then Eric is a big part of that. Second, while the gameplay of BB was never good, at least there WAS gameplay when Eric was around. After he leaves there is nothing but a grind that does nothing but lengthen the game (best exemplified in the RIDICULOUS Lisa grind) then again, it is hard to imagine any way to make the gameplay interesting without an antagonist... kind of shows how flawed things are at their core.