Well you already do lose out on some things by going to war with him rather than making peace, as one would expect. So I suspect you will lose income from the cams, until you can make it up by getting everyone in the house naked and sexually active. Also I suspect that with the fake ID in Eric's wallet, we may find a way to have him fired from his job. However, I don't believe relationships will suffer, as even by 0.4 you are already on the path of winning Mom over, and in my game, Eric has no influence over anyone else; the Aunt has also shown some interest in getting with Mom. In a badly played game, you can miss out on certain relationships, so if you badly played against Eric, I guess you could lose out on Mom content completely.