Personally, I think that endowing a weapon should make the crusader that element.
ex: a crusader uses endow on a vampire dagger, and is now considered
a crusader uses endow on a trident and is now considered
This wouldn't have a whole lot of an effect on gameplay thus far (since few cards act based on element), but two that I can think of is that endowing a neutral or water weapon would make it immune to flooding, and endowing a
or
weapon would make it gain from eclipse.
I think mostly this would be a cosmetic buff, and would make the game more fun.