for one, I'd like to use a decent keyboard GUI in the help example. I wanna have it as part of my tutorial and I wouldn't like to make students download it separately unless I really really have to and there's no other way around it. I don't mind that it's kinda hard and I don't really see how it specially makes things harder for me. Maybe a better point is "hey, what if people just want this and none of the other 450 externals?". That's a better point and, well, at least as it comes as separate binaries one can just grab it.
Nonetheless, it already has a separate repository and I can see the benefit of also having an independent version scheme and a download of its own as a single external over there. In fact, I see that would help when packaging ELSE as I'd just download it and paste into the latest build (I wouldn't have to keep building fluidsynth~ every time).
cheers