If I had my way it'd be like this:
Basically, Kryptonians are much stronger and tougher than human (like Luke Cage).
Having developed/lived under a yellow sun like Kal-El, that means he is charged up permanently because his biochemistry has been altered.
I never liked the insta power loss of pre-crisis. Nor do I care for the post-crisis slow drain to merely human.
I could live with a slow battery de-charge to Luke Cage IF under a very specific red solar radiation that is not synthesizable (ditto green K).
I would see it being bout the same way, as say under the Red Sun or exposed to a big charge of Greek K, would temp revert back to being like Cage for strenght/durability, rest be lkike Spiderman for speed/quickness, and keep his supersenses, but no HV...