The general assembly may from time to time repeal any fee, excise, or tax pledged by Section 2g of Article VIII, Ohio Constitution, to the payment of the interest on or principal of the bonds or other obligations issued pursuant to said Section 2g and sections 5528.10 and 5528.11 of the Revised Code, and enact as a substitute therefor any fee, excise, or tax relating to the registration, operation, or use of vehicles on the public highways, or to fuels used for propelling such vehicles, provided that nothing in this section authorizes any impairment of the obligation of this state to levy and collect sufficient of said fees, excises, or taxes to pay the bonds or other obligations issued pursuant to Section 2g of Article VIII, Ohio Constitution, for which other provision is not made.