Alts should automatically be on your friends list and tenants of your house (without using up a slot) imo. I don't see how this loses SE anything. If anything, SE makes more money on alt characters because pretty much all of the outfits on the online store are for one character only, so you have to buy them again if you want them for an alt. Being able to mail your alts or have them share your home (something they promised us ages ago that hasn't materialized) is just QOL.