I know that you said it was a rhetorical question
Would the opposition have been as intense if the TRNC was simply RNC?
but to answer a might-have-been of history, I'd say no. If the T army had withdrawn in c. late 1970s, or certainly by time Greece joined EEC, and even if a separate republic had been declared, the strength with which one could assert that this (RNC) was not a republic derived from Turkey (as opposed to a republic in which the Turkish language was spoken by Cypriots) would have proved decisive. Anyway, that's my historical speculation.