We couldn't end up in the lower half anyway, I believe, because we've always been aligned apart from Juventus the last few seasons. We actually had competing match days in the group stage last year with Milan, weirdly enough.
Anyway, I think it's a TV thing more than anything why certain teams can't be in the same side of the groups, rivalries or not. Germans will constantly tell you Bayern/Dortmund isn't really a rivalry, but they still were kept on separate sides, for example.
Barca and Inter are a toss up tbh, this is far from a strong Barca side. If Inter play their own football, then they have every chance. The problem is if Inter cant field their best 11, since their backups are horrible.
Bayern are favs for 1st place in the group, but there is little to sepperate Barca and Inter for 2nd.