Cons are a bigger manpower and fuel investment, sorry to say. Well and munitions too. You have to buy the grenade package or risk getting shat on by units in buildings or light vehicles. You don't get 7man until t4 or you spend manpower and fuel to get it earlier at t3. You pay nothing for grenadier squads to unlock their abilities. Nor do you pay anything to unlock VSL. It's based on cp.
Pay nothing for grenadier, I'm sorry try pulling a rifle nade or getting lmg42 without investing 40 fuel. Go ahead do that. let see how it turns out. Why not try a 1 min rifle nade/mg42 too.