I Think the general consensus is that the Omnis found in TRO 3058 are the first-generation, and everything else was able to draw on the lessons of those 'mechs. The rest are a bit blurry...I'd say offhand, any found in 3060-67 are 2nd gen, the Celestials are 3rd gen, and post-Jihad are 4th. That's probably a matter of taste, though.
That's pretty much how I see it too...it makes a good amount of sense for things to be organized that way.
New page, reposting this.
If anyone else has an article ready and wants to reserve a slot, lemme know!
Current Reservations:
cold1: Bowman
Diplominator: Jupiter
Dragon Cat: Mercury II (maybe?)
Empyrus: Hauptmann, Sha Yu, Sling
Fallen Raven: Penetrator
Geovanni Blasini: Chaffee, Quasit
Getz: Legacy
GreekFire: Grand Titan, Savage Wolf
kotetsu: Vapor Eagle, Rifleman IIC, Warhammer IIC
marauder648: Raptor
Moonsword: Templar (maybe?)
The Eagle: Hammer
Current requests: Black Hawk-KU, Brigand, Celerity, Conjurer, Crimson Langur, Hammerhands, Parash, Snow Fox, Sunder