Cruise ships aren't bad options either. I hear they're a bit underutilized
They’ve never solved the sanitation problem. But perhaps small changes could be made to future ship designs, to allow them to be re-purposed
Or, maybe just to make sure they are not super powerful disease spreaders on normal times.
I imagine they are hard to regulate, but a country can make some seal of approval, and maybe even punish people seeking treatment for transmissible diseases after they come from one without the seal. (Even tough that second one is very heavy handed and hopefully unnecessary.)