Mounts and Companions take quite a bit of time to level. Getting them to high levels is quite the commitment. So when you get a new one and start at level 1 it really pushes me away from actually using them. Why bother spending all this time using a weak/slow creature when I could be using a better one and get them more XP?

So my idea is to be able to spend money at stables to level them up, Perhaps only being able them to the same level as the highest level critter in your collection.

I think this would more easily let players use the other mounts and Companions without a huge time investment. It would be nice quality of life feature.