Probably rifles and pistols, and their future analogues, would be what the Founders had in mind for individual possession, with field pieces and their equivalents being held in local Armories. So today that would translate to lawful ownership of basically everything (to include automatic rifles) at a scale below explosive devices such as grenades, mortars, missiles, artillery and up. What more would be needed to mount a successful insurgency by the bulk of the populace against a tyrannical government?
If my history is correct, the colonies needed the privately owned warships to win the revolution.
Someday, we may need the same size of weapons.