"Third gear" doctrine of state labor law?

Asserting that a state labor law setups (replicating) conducting union certification elections and (uniquely) forcing employers to actually bargain with the union -- do not violate federal preemption on the theory that you cannot preempt something (enforceable) labor law with nothing (unenforceable) ...

... (assuming this holds up in court) this sets up a very tricky future for the courts. Every time federal labor law morphs -- the enforceability and practicability of fed law might need to be judged all over again to decide whether state setups may continue to operate (not be preempted).  Pretty wacky state of things.

Given that states may add enforceablity to current federal law (e.g., by making union busting a felony);
Given that states may add to their current separate certification setups (today, for farm workers) any classification that the NLRB combs out of federal definition of employees (tomorrow, graduate student instructors and college athletes -- NOW THAT IT OCCURS TO US THAT WE CAN DO THIS);
Given that states can replicate the entire federal setup as long as the federal setup remains a road to nowhere ...

... it seems state and federal labor laws could be approaching pretty closely meshed.

For the sake of workability it might make sense for courts to allow, for instance, states to set a 7 day election requirement to for an election after card check -- to supplement a (theoretical here) 30 day federal requirement.

Could call this a "third-gear" doctrine.

At this point there might not be much light showing between state and federal labor law jurisdiction.  Maybe courts could bring on the final meshing by, say, not allowing states to overrule a finding in favor of certification -- but allowing states to overrule a finding against certification: a relative of can't preempt something with nothing.

Not perfectly clear doctrine, but we have to do something.