Dukhat, I dig what you wrote here about conjectural classes and it got me thinking about why the Ambassador class had only a short run. Since it appears that Starfleet tends to introduce a new design (or designs) in small doses then builds them in bulk once they become standard issue, if we look back to that time that the Ambassador class was a new design we know that the Miranda's and Excelsior classes were being built in bulk (during the 10,000-45,000 registries). Now we know that by the time of the Dominion war the fancy new classes were the Sovereign, Nova, Intrepid and Defiant types with the Galaxy and Nebula classes filling the next wave of standard run type ships (at roughly 60,000-80,000). Where things go wrong is the time period when the Galaxy and Nebula were new and during the period of 45,000-60,000 instead of Ambassadors being built in bulk, we see Akira, Steamrunner, Niagara, New Orleans, Springfield, Challenger, Freedom, etc. which are all new, but not really capital ships.
So it seems to me that the Ambassador never got a second run and instead a large influx of other more advanced classes took over as the bulk of the fleet around that time. While in my opinion the real world reason for this seems to be that the show producers had access to the Akira, Steamrunner, Norway, Sabre, etc. designs and didn't have a cgi model for the Ambassador, the ships role became limited due to circumstance. This is of course assuming that the Akira, Steamrunner, Norway and Sabre classes are in fact older than the Galaxy which is arguable.
That said I have pondered recently that it is possible that the Ambassador may have had a second run somewhere in the 45,000-60,000's we just never saw them due to the model not available to the production staff. While there isn't much evidence to this claim I ponder that the USS Princeton NCC-59804 was such a ship having Ambassador type components with updated nacelles. It also makes an argument that there may have been a flaw in the Ambassador style warp nacelles or at the very least were less effective than the Galaxy style bussards. So who knows there may be Ambassador variants out there with 50,000+ registries and newer warp nacelles as well. While there is no real answer I respect your opinions based on what you write in this column so wondered what you thought about this?