Sidegrade, "SIDEGRADE". They're included in tech, which the cost of is conveniently included in OKW's starting resources (40 fuel). Molos have a sidegrade cost to unlock at HQ (can't remember how much) which is independent of teching.
But yeah, longer throw time and nil/less damage on impact would be good for both.
Edit: Longer throw time on the incendiary nade, not the molotov lol.
The damage on the impact is fine, the throwing time is just too short to have a good reaction on them, which means you will lose atleast 3 models. Also I never hear grenade on impact when playing allies.