All of those issues would be fixed if maps were made with realistic engagements in mind.
Such as Berezina. That has fairly realistic engagement ranges, and is a perfect example of a map where rifle grenades would come in very handy indeed. The only issue is the fact that it is set in 1941... but the point stands.
We SHOULD be able to do some of the parts manually. Namely cycling out an unfired round, and loading individual rounds in bolt-action rifles.
German rifle grenades, apparently, had no minimum range; if you fired them at a wall five feet away, you'd get cooked. Russian ones, on the other hand, had an arming distance of 140 meters. That gives you an idea of just how far away most engagements were in WWII. Infantry fighting from the farm/hill and the town in Ogledow is generally the range at which rifle grenades would be deployed.
By the way, they don't take much time to reload at all. The only thing that is at all time consuming is attaching/detaching the device, and that is fairly quick.
Keep in mind that implementing rifle grenades doesn't mean they'll be on every single map. At the moment, implementing them would sort of go to waste, considering just how few map have true engagement ranges.