Sharpshooter vs GWM

[MaxWilson]

I can imagine crossbows being relatively difficult to reload while prone/sitting. Kneeling clearly works, as Pavises were a thing. Slings... well, the less we think about it the better, I suppose.

David Weber's books have given me the impression that you reload it by lying your back and cocking it with your feet, before poking your head up out of your ice hole to shoot again at the Temple Guardsmen. Seems reasonable but I don't know if it would work in practice. In any case, that's about reloading instead of aiming.

Maybe crossbows should have a ROF penalty while prone instead of disadvantage to attack rolls?

This does mean that you'll see a lot more ranged creatures stay prone throughout the fight to avoid incoming fire while shooting back, but I don't see a problem with that. There are a lot of mobility options for melee characters, and a not a lot of reason to use those mobility options, so perhaps a Monk engaging on a group of archers while they're prone might be a good play.

I agree that it leads to good play. Generally I feel like anything that helps justify the existence of melee characters is a good thing. If someone is lying prone to avoid missile fire, presenting a melee threat is one way to punish them for that.

That said, most of my tool-using bad guys are not disciplined enough to do that kind of thing. Mostly just scro and hobgoblins. (Maybe I should add drow to that list but historically I haven't played drow as disciplined team fighters, rather than chaotic individualists.)