I agree. I like that its one spell from lvlx-50 and it gets more powerful as you level. Would be sweet if the spells changed a little as you leveled. 1-20 would have a certain look. 21-40 a little bigger and so on.

Could be said that right now you already have that. example being that each lightning spell looks bigger and better, I think you're referring however to how the MP costs increases with level and so does damage, so why not the look of the spell in particular since its after all more powerful at 50 than it was at the level it was first obtained. To be fair spells learned in the 40+ wouldn't really change in look as they are already higher leveled spells, or maybe just one change for them at 50. Interesting idea though.