A way to effectively balance things: Mass, volume, and density.

[Admiral.Piett]

I believe accurate mass calculations to be a must to sort out the biggest issue the game has: Movement. They have chosen their flight model, and they need accurate representation of mass to make it as flexible and balanced as possible. HP pool should be directly proportional to mass, albeit added in sequence per amount of mass per material (Plexiglass adding less HP, decorative blocks adding 0 HP, and making shapes add a proportional amount of HP according to their mass makes a lot of sense.