I plan to stay on Frostwolf regardless, but if there is a TBC server I'd say stick with the normal Warmane model for it. Lordaeron is already there for those who want the purist, x1 experience, and it would just draw players from it to have a similarly grindly TBC server.
I will say that making a TBC server makes WAY more sense than a WoD or Legion server, for the simple fact that a lot of people are interested in playing TBC. Other private servers have come out with either WoD or Legion servers, or have announced plans to, and I see no hype or even mild interest about those servers on the private server forums. Retail now has the WoW token to allow people to play for free, so a lot of players who would otherwise be interested in private servers for Legion can just play retail.
With TBC, by contrast, anytime even a buggy as can be server is announced, there's huge interest. Only makes sense to open servers in the expansions where there's interest.