I've definitely found myself wishing that the buff hammer would give me the same 30% health to the balloon to which it gives the hull. Or same with the front gun on a goldfish, etc.
Perhaps keep the buff hammer purely a buff to a components main purpose- speed, maneuverability, damage, vertical movement, etc. and make a reinforcement hammer that just boosts the health to whatever component is being sprayed.
As for making this not instantly OP, I'd say leave buff hammer values alone, and make the reinforcement values less all around, or last less time. For instance- only give the balloon an extra 20% (only enough to outlast the double carronade, no more), or same with a gun, just barely enough to keep it up after an artemis/hwacha strike.
How we would make this a working concept in terms of what this tool supposedly is...? No idea.