It's the first time that I played Big Brother, never played the original version by DS, but I start to see why he abandoned it back then.
As soon as you remove Eric the game lose its charm. Eric is MC's motivation to move on and do the things he does to get into the girls pants.
The 'Sex ED' together with peeking on Ann giving Eric a BJ while watching TV are by far the hottest scenes in the game.
The plot around the dating website/hackers and Ann's goal to cheat on Eric feels a bit dumb. Because as mentioned above, Eric is the force that keeps MC going. Without Eric the game turns into a 08/15-harem game where MC goes around and fucks everyone.
I would had changed the plot and go with the wedding proposal as mentioned in of the dinner scenes early in the game. I also would change MC's behaviour towards Eric and make them actual friends. MC should feel happy for Ann at first when Eric starts to corrupt MC's entire family and himself. Thanks to Eric's corruption and manipulation MC starts to desire the girls around him.
Eric should marry Ann and move in and slowly and steady corrupt everyone around him into sluts. It also should be Eric's idea to have Ann sign up on the dating site. Later Ann will meet her dating partners at home where Alice and Lisa would join as part of their sexual education.
Eric's betrayal is what breaks their friendship but by then everyone around MC is far to far into the rabbit hole and no one will believe MC. He needs to come up with a plan that will convince everyone that Eric is a liar and a pretender....
Anyway, sorry for the long post, but I had to get it off my chest to be able to move on.
Keep up with the great work.