1) pretending like the goal of government is to not give people control of the services provided is fallacious. Just because you currently can’t “define the terms of service” for the US military (which I think in itself is up for debate) is a critique of the currently establishment, but not of the idea as a whole (state and taxation).

2) even if the terms of service could be defined, that matters very little. If all of your neighbors pay a private company for military protection, you now no longer have to pay for it, because you get de facto protection from your neighbors. That is a very bad incentive that you should not be arguing for.