summoning it for a certain amount of time kind of ruins the mount thing, but applying a celestial or half-celestial template for a certain amount of time per day sounds interesting.
Then again, how much time, and would the abilities or the time increase with level increase.
Just thought of something, mabye something like a holy barbarian rage, where the paladin turns into a half-celestial for a certain number of rounds equal to 4+the new CHA modifier or something like that, and with the increase in paladin level, an increase in times per day?
The character of mine that doesn't want the mount thinks this is a bit too short, but I dunno, any thoughts?