That's the absolute worst way to balance any 'consumable' item.
You end up with an
Elixir scenario: An item so rare(and powerful), that you never use it in case you need it more in the next fight.
I agree and in general there is nothing wrong with that imo. Consumables always work that way anyway (or they are pretty much meaningless or weak). Grenades are just own option in battle. If you can manage without them there is nothing wrong. If you save them up for later there's nothing wrong with that either. Imo there should be a good chance to restock your arsenal but only to certain level, determined by general scarcity of grenades and ingredients to be found in the world and at merchants.
Ideally, those items should be available for every fight(specifically because they are there to cover for weaknesses of your deck), especially if you make the effort to bolster your stock through crafting or purchase.
Nothing wrong with that. Rare doesn't mean that you only find one granade every 10 hours. It means that you have only a limited number of grenades no matter what.
For the sake of consistency with the Memory deck system, there should be at the very least a soft cap on the number you can effectively deploy in a single fight(how many you can deploy in general is already soft-capped by the supplies you can find/buy).
I don't see the issue. The supply of grenades was already pretty scarce in the EA version. There is no need to further limit them for single encounters imo. And the more you progress in the game the less powerful grenades will get anyway. At the end of act 1 and intensive exploration I had perhaps 20 grenades and I only used a few in encounters. I would say that they are indeed kind of rare and that you're not spammed with them.
And there is also no consistency issue here imo either. Consumables and skills with cooldowns are different breeds with different pecularities. The only scenario in which your belt would work is one in which your consumables stock pretty much automatically refilled after battle (think somethink like Witcher 3 potions). But that would really be inconsistent with the whole rest of the Divinity world and its overall systematic design.
