Perhaps padded covers for when they are not in use?
But they will likely get lost or stolen or sold too.
The advantage of the top rail is the ability to have multiple scopes fitted so you can have your normal scope at the rear with a night scope in front of it for use at night without having to rezero, and perhaps a magnifying scope in front of that for longer range use, and if you take all those off fold up iron sights in an emergency.
The issue of comfort will be the front side and front bottom rails, with the bottom rail being used for lights or lasers or front pistol grips or bipods or combined pistolgrip bipods... these would all get in the way of the standard under barrel grenade launcher.
Torches and lasers and other bits and bobs can be mounted on the sides of the front of the rifle too, though your average soldier probably wants a decent, light scope and the option of a front grip/bipod, perhaps with a torch and laser built into it or a 40mm grenade launcher. Being able to also mount night optics and long range magnifying optics on the top rail would be a bonus but the side rails will probably not get used much except to hold torches and lasers when the underbarrel grenade launcher is fitted.
For most soldiers a low powered scope and a grenade launcher will be all they need... and for that a top rail might be all they need.
Perhaps a new rail design that has multiple attachment points built in to the rifle so for instance the side rails might have 6 recessed attachment points along the side of the rifle so that when the rails are removed the side of the rifle is just like the standard AK-74M stock and the same with the lower rail.
The 6 attachment points makes the rails rigid and secure when fitted, but the recessed attachment points don't get in the way when the rail is not fitted and it is like a rifle with no rails when the rails are removed. Both the side rails and the bottom rail would be removable with the top rail fixed in position.
The rails can be fixed to the rifle when the attachments are issued, so when a bottom mount pistol grip is issued it comes with the bottom rail. The rail wrench can be part of the rifles cleaning kit.
If a 40mm grenade launcher is issued then you wont get a rail as it will not be rail mounted. Side mounted equipent will come with both side rails of course to allow a choice of side to mount it on.
Anyway... I would expect they might issue "hotter" 5.45mm ammo with the new rifle, but I doubt they will go for a completely new calibre.
The new modular weapon might even include a marksman rifle to replace the SVDS.