There seem to be several groups of "stablemate" starship types, representing (roughly) the Heavy Cruiser, Light Cruiser, and Fast Cruiser classifications:
Constitution/ Miranda/ Constellation
Excelsior/ Centaur/ ????
Ambassador/ ????/ ????
Galaxy/ Nebula/ ????
Sovreign/ ????/ Intrepid
Time-wise, does this seem correct? Does anyone have suggestions for the classes represented by the ????'s. Can anyone think of "reasons" I can use in my game why the Constellation and Miranda classes are still so common while equivelent vessels from the Excelsior and Ambasador eras seem so rare and the Ambassador apparently isn't in commission at all?
Unless someone posts something really obvious I haven't thought of, these classes are what I plan to go with in my campaign... Starfleet will be reactivating many mothballed Constitution, Constellation, and Ambassador class vessels, and calling up many retired officers, to fill the gaps in the line. I've always thought that Starfleet, even just considering the "canon classes" seen on screen, has too many ship types for reasonable logistics and crew familiarity. I plan to narrow it down for my campaign with Starfleet built around the above classes and a few other specialty classes (such as the Oberth and Nova).
I've always thought it interesting that the Constitution Class was considered so successful, yet there are dozens of Mirandas and a few Constellations still in service in the TNG era and no Constitutions to be seen.