There are no real problems with the Greek in any of those options, Soy, so I think you should go for what you really like. Tattoos are definitely not my thing, so I'd personally have trouble working up enough enthusiasm to make a choice.
As for eliding the "ε" of μήποτε, the Greeks would certainly have dropped it in speaking, but just as certainly would have included it in writing, so that one's up to you, too ...