I still think the best solution is having free grenades with a timer that are either on autofire or an activated ability. that take up a weapon slot. They'd be primarily for garrison clearing (especially/mostly mgs) and soft countering cover by forcing movement, and the fact that they have a somewhat lengthy timer, take up a weapon slot, and lock out flamers and minesweepers would keep it balanced IMO, especially considering their carbines are pretty bad (as in can't beat anything 1 on 1 with all four, let alone 3).
But Rifle Company flamethrowers and Assault Engineers already fulfill anti-garrison purposes.
Not to mention that 2 or more RETs with this auto fire grenade could deny garrison alternately firing rifle grenades and basically make riflemen grenades redundant.
So basically, to reiterate, it wouldn't be as bad as Coh1 because there's only one, it has a decently long timer and distinctive audio cue (if it doesn't bug out like riflenades sorta do), the rest of the squad is pretty combat ineffective (unlike sections from Coh1), and it locks out other useful upgrades and a weapon slot. Having it as an activated ability would also make it much harder to blob REs in the way Coh1 sections were.
Why would anyone pick the rifle grenade that's easy to dodge when they could pick the flamethrower that's not dodgeable. Not to mention that if the rifle grenades are too easy to dodge the RET squad isn't doing any damage and is back to combat ineffectiveness. Normal riflemen grenades are already easy to dodge.
And there is a trade with giving RE's a grenade launcher via that they can't use minesweepers or flamer and it takes a weapon slot. RE's currently aren't attractive in a combat role outside of flamers and bazooka's as while you can put BARs on them that's 120 munition on a unit that is less combat effective than Rifles which only cost 40 more MP to purchase and 3 more MP to reinforce (28).
I think RETs are weak enough that they don't need that trade.
The suggestion I've made is something Rifles can't do which is garrison clearing without using munitions every time and in a more unique way. I'd use RE's much more if they had this type of grenade launcher as Rifles wouldn't have access to it.
Introducing an anti-garrison ability that's not flamethrowers or mortars could upset the balance by a large margin.
Yes RE's don't have much combat power but you can still put one BAR on them if you feel the need to but the grenade launcher is meant to counter garrisons and unit in cover in a way Rifles can't do without spending munitions and having to get closer. They won't have much combat power but this is the trade off to have more utility.
Except the USF isn't lacking in anti-garrison abilities (some would argue they have too many). I think the main issue at hand is that the RETs are completely lacking in direct combat effectiveness, and giving them a Grenadier rifle grenade ability would give them just enough offensive ability to not be useless.
Well the whole point, as I stated in another post, is to make USF build more versified and in a non doctrinal way. If the grenade launcher costs munitions each time to use then it wouldn't be worth it as you might as well use the grenade from Rifles or the USF mortar. The point is to make them a mobile light fire support for your Rifles that doesn't munitions each time and fill a role that Rifles couldn't do already.
It would probably be easier to make USF more diversified if the starting unit was a rifle squad and each tier didn't automatically come with an infantry squad but had reduced cost.
Mortars already fulfill mobile light fire support. It's generally better to use a dedicated unit like the mortar than try to turn another unit into a watered down version of it.