Then I'd like to see someone sue because progressive federal taxation violates the equal protection clause.
Affirmative Action violates the equal protection clause.
Any Federal program that tilts the playing field, to achieve equal outcomes, violates the equal protection clause.
The insidiousness of the 14th is not just what it does to the states, but to the duplicitous hypocrisy it allows the Federal government to engage in. You can tell it's a product of Congress, for Congress.
Lets get portions of it repealed. I've given a lot of thouht to it, and I think the best attack on it would be to make it unenforceable by the Federal Courts - but it would be enforceable by State Courts. Essentially, the equal protection clause would be written into every state Constitution, but not the federal one. The mechanics of this have precedent in the 11th Amendment, which takes US judicial authority away from out-of-staters, when they sue a State.
I have a dream that one day the ACLU would have to win 50 "equal protection" lawsuits, whereas now the 14th allows them to just win one, in order to control the entire nation.
My route of challenge to the 14th would be for a state to forbid any private or government entity within it's boundries to accept any federal monies without the specific consent of that state legislature.
Since the 14th outlines only "state" infringements another route would be to allow state appelate courts simply "not to hear" certain challenges as in the federal system. This would preclude a basis for the complaintant eg. no state position; no violation of the 14th.