The other day I was looking at Romulan ranking conventions according to both FASA and LUG and I was trying to compare them from what we know from the TV shows.
FASA's system is :
Equatoriam
Secundam
Trinam
Centurion
Sub-commander
Commander
Equatoriam is the basic rank that all hold when doing their military service. Then the equivalent of NCOs/junior officers are secundam/trinam. Then centurions act as dept heads and sometimes 1st officer IIRC. Sub-commanders are the equivalent of Starfleet captains and commanders = admirals.
LUG has the following convention:
Uhlan
Sub-lieutenant
Lieutenant
Sub-commander
Commander
Centurion
Admiral
Ulhans = Starfleet ensigns. Sub-commanders and commanders are roughly = dept heads. Centurions = captains, etc.
Yet from what we've seen in TOS, TNG and Nemesis *all* ship commanders were all sub-commanders or commanders. The only centurion that I can recall is the ship's first officer in 'Balance of Terror'. Then in 'The Enterprise Incident' the female Romulan officer in command of 3 ships is a 'commander' and her direct subordinate is a 'sub-commander'.
The fast-forward to TNG in the episode 'The Neutral Zone' where we catch the first glimpse of TNG-era Romulans. The two officers on board the Warbird are titled 'commander' and 'sub-commander'.
Then in 'Contagion' the Warbird's captain is 'Sub-commander Taris'. Later in 'The Defector' Tomalak's rank is established as 'commander' and Jarok reveals himself to be a Romulan 'admiral'.
In 'Data's Day' I'm not 100% sure but I that the Warbird's captain and the Romulan spy posing as a Vulcan dignitary arr introduced as 'commander and sub-commander'.
Sela is also called a 'commander' but her 2nd in command is called some gorund force rank like 'major' or 'general'.
In 'Face of the Enemy' Toreth is called a 'commander', N'Vek is the ist officer and is called a 'sub-commander' but Troi's Tal Shiar agent is a 'major'. Then in 'The Pegasus' the Warbird's captain is a 'commander'.
Finally in DS9's 'The Die is Cast' there's a Tal Shiar 'colonel', and in 'Nemesis' Donatra was a 'commander'.
This is far from an exhaustive list but we se a common pattern emerging. It seems to me that FASA was more on target than LUG was.
So we have no idea what the lower ranks are, but the mentions of 'commander' and 'sub-commander' seem to pop up regularly as being the equivalent of commodore/fleet captain (officers in charge of small fleets/squadrons), captain and 1st officer. The most senior oficers are 'admirals'.Ground forces/intelligence personel use the amry's ranking conventions such as 'major', 'colonel' or 'general'.
How about merging FASA and LUG's conventions together with a few twists? Here's what I had mind:
TROOPER - basic rank
LEAD TROOPER - NCO
UHLAN (I like the term, sounds neat) - ensign/senior NCO (backbone of the fleet)
SUB-LIEUTENANT
LIEUTENANT
CENTURION - somewhat equivalent to Starfleet Lt CMDRs; dept heads.
SUB-COMMANDER - 1st officers to captains of single vessels for less than X years
COMMANDER - captains of single vessels for more than X years to leaders of small fleets/squadrons
GRAND COMMANDER - equal to Starfleet admiral; often interchanged for the term 'admiral'. For instance, Romulan Grand Commander T'var would introduce herself as 'Admiral T'var' to a Starfleet captain.
Ground forces/Tal Shiar ranks could be :
TROOPER
LEAD TROOPER
UHLAN
SUB-LIEUTENANT
LIEUTENANT
CENTURION
MAJOR
COLONEL
GENERAL
I don't like the terms 'trooper'/'lead trooper' but that's the best I could come up with. what do you think?