That would work, but would make the early game for a rogue hard since it pushes the player to invest in the grenade skill and they may not be able to get that straight away.
Well, that's a balancing issue. I can't say too much about that without knowing each and every skill available for the rogue at various levels.
And of course the rogue could still use normal grenades. I just don't think that you should have excessive numbers of them art your disposal. If the rogues uses one, two or even three in one encounter, it's imo fine. That should be doable with a bit of exploring and a bit of shopping. But an inventory full of grenades is imo negatively influencing the balancing too much for the whole party.
