i see potential.
unfortunately, i think infecting zoro with the plague is no longer a viable option, because zoro has been in the live floor, and the air within the dome is filled with antibodies completely neutralizing the plague from being used a second time, which zoro should've inhaled in.
even if zoro got infected somehow, i still don't think he will ever succumb to the ice oni's mind control, his willpower is far too great for something like that to happen, resisting the ice oni's for an hour should be easy.
and there'll be no need for sanji, because zoro can just set his swords ablaze with his foxfire style, and keep himself warm until the antidote is made.
the safest method to heal zoro (a truly nightmarish scenario) that's is available in onigashima is orochi's devil fruit, that would give him 7 additional lives, but that's so unlikely to happen because oda stated that he prefers zoro to remain without a devil fruit.