Something to think about. Surprisingly it's my two DILs that like the idea the best. We could all have our own space but share barn, pastures, pens....
If you situated the houses in a way where your back yards were all private so you had your own space, and they were the furthest apart they could be. Then had the horse pastures, shelters etc in the middle, with gates from all sides it would work out great! You would all have your independence but also be on hand for emergencies and riding together!
Maybe we should all sell up, by a massive acerage great for riding and start a Saddle club commune! : D