Personally I think a better solution would be mass issue of specialist grenade rounds/mini launchers like the XM 18-22, which shoots 18 22lr rounds out of a standard 40mm under barrel grenade launcher.
The Ukrainians probably don’t use them because of the ridiculous cost and comically low availability numbers, but I’m pretty sure you can find any number of manufacturers in China who can pump out clones in silly numbers at affordable prices. Especially if these are only rated to be single use disposable rather than being reloadable.
Rate of fire might be low, but each of the 22lr rounds will have its own barrel (rifling optional), the range should be pretty respectable since spread will be minimal.
The benefit of this system is that you can use it with standard issue UBGLs, so the costs of issue will be minimal from both a budget and weight pov.
Since there will already be soldiers from each squad who have UBGLs as standard issue, you can roll this out en mass in a very short timeframe. And all your grenadiers will still be able to use regular grenades so there is very little opportunity cost other than monetary.
