88 Flak allows for all ships in the game to be flown. 88 Flak actually takes this to the logical extreme and everything in the game is flyable. Transports, Capitals, even Stations and Weapon Platforms can be purchased and flown. However, I'm not sure if you're looking for a vanilla FL style gameplay experience.
88 Flak is a pretty drastic departure from what vanilla FL feels like. It's much faster, and the combat is brutal. The ships are all balanced such that each class (light, heavy, etc) are each given different roles rather than one being just plain better than the other. Flak is designed around playing with friends, as the combat in general requires teamwork between different ships. I'd recommend giving it a shot, even if it's not for everyone.
Download link is here: http://www.memes.no/88flak/forum/viewtopic.php?f=1&t=114