Lots of civilian and merchant starships are old tech, even in the TNG period. For instance Faro's freighter, in the TNG episode "The most toys", has a plot stated maximum velocity of Warp 3 (27c) so was still using TOS / TMP warp drive technology.
A pre-TOS Lyran fleet would be something to envisage. I run the stock SFC 1 Lyran fleet as TMP models, having the correct SFB TOS era ships represented in my version of the game.
Being able to stage early Kzinti / Lyran battles, maybe from before the time of the Kzinti Usurper, would be interesting.