The motives here are so transparent. The Federal gasoline tax is the only tax that falls disproportionately (relative to Federal expenditures) on rural states. In every other area of Federal taxes and expenditures, rural states are overwhelmingly classified as "recipient" states instead of "donor" states.
I'd say lets call their bluff on this one. Every state will be guaranteed to get back at least 95% of what they pay in Federal fuel taxes, and every state will get back at least 95% of what they pay in income taxes. Heck -- let's throw FICA and Medicare taxes in the mix for good measure.
What you're suggesting locks the federal spending in each state to a narrow range of what they contribute. That seems an artificial constraint when the need arises to concentrate on a project that logically needs to exist in one, and only place. How many NASA space centers do you need? Shall we spend an equal amount on our military bases for our armed forces in each state regardless of the military need for them? Why should we build one in Vermont?
I think the best way for us to accomplish what you're suggesting is to dissolve the US into 50 countries, and let them work out whatever treaties they want, if any.