Either that or, you must allow someone who has done whatever to pledge his support to withdraw it if the government fails to live up to its end of the bargin.
I see the present Constitution as just such a system, short of a formal declaration of support. The government has failed to live up to its end of the bargin and it's time to either change it, or withdraw from it.
I, personally, feel that many have already done that. In my eyes, that is the reason there are over 100 million eligible voters out there who don't participate. The only thing is, the government will not allow them to withdraw and it forces them to continue to support it whether they want to or not.
How to make a change such as you suggest is the question of the day, I guess. It would almost take a completely new government from the top down to make that kind of change, along with some major changes to the Constitution, if not a new constitution.
Such a system seems like it could be workable, but there would have to be some very strong protections for anyone who chooses to participate and for those who choose not to participate, as well.