None of these look like the sort of legitimate use cases Solarius asked for.
Elevators can already be blocked off from missiles - TFTD alien city elevators come to mind as an example. Never mind that I fail to see what's so useful about this idea.
More frequent use of melee weapons can be encouraged by making those weapons more attractive/powerful, or replacing (some) AI grenades with melee weapons. Or other balancing methods.
There is no 'realistic' reason I can see why one can't use a grenade at point blank range. Just don't grip the lever, grenade will go boom. Or shove the other guy with one hand/shoulder while covering your grenade-dropping/rolling with your body and doing it with the other hand. It's miles easier than hitting the enemy at the same range with a melee weapon or even a handgun. Your oppisition needs to be much bigger, possess eight hands or something like that to actually have a chance to counter that.
CQB is supposed to simulate 'gun kata'-esque dodging, shoving the barrel slightly offline, etc. None of that really helps against an exploding grenade that's omnidirectional and lethal to at least about 5 metres out. And doesn't really have the initial velocity to go awry in the same manner as a bullet or other projectile fired from a gun does.
I might, of course, be missing something here. If so, do give an example.