couldnt gambit charge up mjolnir if he had it in his possession
That is a great question, which ironically leads to another one. Is Gambit worthy of wielding Mjolnir? Has he ever been near Thor or Mjolnir, let alone try to pick it up? I don't recall but if someone knows, that would help.
I would take a wild guess and say he couldn't, because Thor's weapons are really "fail-safe" and defensive, even if someone else uses it. It wouldn't be subject to the energies of Gambit or even cosmic blasts for that matter.
Yet....I could be wrong. It would be frikkin' awesome though if Gambit could charge it. Can you imagine the power and energy it would produce?