I was wondering that if when you get to a surten amount of days at BK that maybe you could get an upgrade for your stable space. just an idea (Angel can diside on the number of days)

There are already quite a few ways to get more stable space: Building up to the 4th/5th level of the Stable nets you 200/250 space, then if you buy the Expand Stable Scroll, that's another 10 space.

There are also a number of ways to earn the scroll such as: placing in the Exhibitions (that haven't been running), buying from other players

Lastly, your idea is kind of already in the game: by placing in the Weekly Charts, you earn 10 gold for each you place in, allowing you to buy the scroll if you place in 2.