I tested for a while the other night, and whislt playing, i unexpectedly fell out of SSJ form......... quite a surprise at the time actually. I found myself having to escape the fight scene in order to raise my Ki enough to Ascend again. All in all, its a great addition to the gameley, and along with other things that have been implemented, adds a REAL strategy aspect to ESF.
That said tho, My opinon [i said opinion! no flames!] re: non saiyan characters is that they should be able to descend at will, even tho they wont be descending due to Ki loss, it would still add an extra element to a game that is overflowing with awesome gameplay as it is.