When I make alts, horses suck. I'm used to 50% speed. I end up with 15%. It takes forever to get a decent mount again.
So, my suggestion is to make an account-wide system to make alts easier to get good mounts for.
Each type of horse would be independent in this system, so if you improve an imperial edition horse, it won't apply for any horse except the imperial.
So, say I upgrade a horse to 50% speed on my main character. I buy that same mount on my alt. Now I simply suggest the daily feeding period be ignored up to the level that was previously reached, allowing you to outright buy your way to the same level on alts.
Say my horse was level 30. My alt can now buy that same horse and upgrade it straight to 30 by paying for upgrades. At that point, the waiting period kicks back in and I must wait a day to upgrade the horse again.
I'd even go as far as to say it would be fair to raise the price from 250 to maybe 400 after the first feeding every day, so people could choose the inexpensive daily feeding or pay extra to get levels faster.
Of course, the first time leveling a type of mount would take as long as it currently does and would still only cost 250 daily.
I think this would make playing alts a bit more rewarding (or at least approachable), and it would also provide a new gold sink, which seems to be needed.
EP: Slania Isara : Harambe Was an Inside Job