Sometimes, especially for your first mechanical keyboard, you just gotta get the one that you've got your eye on. If he really wants a full-sized Otaku FC500R, then he might as well get it.
I have a Leopold and it was all right for a first mech kb, but I wouldn't buy another. Especially the 500, which uses an even weirder spacebar than the other Leopolds. Even the "universal space bar" won't fit it, I think. If he ever wants to change his keycaps out, that will be a problem.