Compared with a modern military "citizens with guns" are really nothing more than rock-throwers. (And you're right, this can be effective: Afghanistan is a great example of organized rock-throwers prevailing in the long-run)
It seems to me, the idea of the United States ensuring its citizens retained weapons was to achieve what you're describing: equality, and equality between the people and the people chosen to govern; not allowing the appointed governors' access to fire-power make them superior to the people. This arrangement is a last resort of sorts to ensure the governors were acting with mutual interest in the nation, instead of launching out to oppress individuals because of the power of their position
I disagree that attempting unilateral disarmament is going to help. Enforcing an artificial constraint on what constitutes appropriate arms is asking people to lie to themselves: for example that a literal rock with enough people is effective in keeping the governors with BlackHawks and cruise missiles from making oppressive choices.
We are barely adequate to this end. If anything we need more power equity, not less.