There can be two "easy" ways to keep most TOS fans happy (in my opinion).
1) Fleet Exeter cruiser (as mentioned before by someone else), greater handling, lower hul/crewl than most fleet cruisers.
2) TOS era texture/skin pack. How hard would it be to make a new texture for the ships that can give it that TOS look/feel? Sell it for, I dunno 2,500 Zen? Get all of the ships re-skinned to
TOS look, that grey hull, black letters, sensor dish (where applicable) and old style nacelles and pylons.