A strange handicap in this game is the stable/horse limit in this game as you can only own 4-5 horses at a time. This makes absolutely no sense because A. There are 19 horse breeds and several have unique skins, and usually have more than 1 unique skin and B. There are 7 different stables which can each hold 3 different horse but Rockstar decided that stables download your horse into a stable network and you can only have 3 horses in the network. Essentially I have several ideas to increase horse limit
1. Individual horse stable: Each stable can hold 3 different horses(Ex: Valentine holds an Arabian, the beginning Tennessee walker, and the raven shire meanwhile strawberry has a turkoman bay, a different arabian, and Brown Jack)
2.Buyable stable slots upgrade: This can go along with the first idea, essentially you can buy more stable slots at a stable which could be universal(like base game) or specific(like first idea)
3.Beecher's Hope stable: During the epilogue, as john you are able to hold far more horse than you are currently able to ie 1. This could be remedied by making Beecher's Hope its own stable or by allowing more pens be horse pens.
I should also address another part of the topic, online horses. I believe that online unique horse should be added to the story mode and its a damn shame that they aren't. This could be its own separate topic but I'm talking about it here because I kind of want to use this as a general horse mod topic. A way someone could add online horses is via the Red Dead Offline mod which I hope is one of their future updates. Another way is by adding them to stables around the world and incorporated in a horse limit increase mod or be its own thing.