FYI. in my mod Divide and Conquer, I went for Commander instead of Captain.
I didn't go for Commander of the Dunedain because simply its a mouthful, and though I was sort of forced to put the whole thing on for Aragorn (can't just call him Chieftain).. I did feel that Commander Halbarad gave a nice ring... as Commander can be something other then a direct rank (even though Captain can as well) I felt it differentiated it from the standard map Captains.
I also went for Goblin King, and Goblin Chief taking after previously mentioned Goblin/Orc leaders of the MM.
I couldn't find anything that was appropriate for Isengard or truly lore worthy. I thought about titles dealing with War, Warlord, Warchief, Warmaster type stuff etc.. for a while until I settled with Uruk Warlord, and Uruk Marshal.
I thought that the added 'Uruk' really showed that it was a military styled command - and thus that the true leadership was not with them. Though I suppose it is really preference.
I added a lot of new factions to my mod and spent a long time thinking about their names...
Faction list is..
Portugal- Lothlorien
Egypt - Rivendell
Denmark - Lindon
Mongols - Woodland Realm
timurids - Belegost
aztecs - Khazad-dum
moors - Erebor
russia - Rangers of the North
turks - Bree-land
sicily - Gondor
milan - Rohan
scotland - Dale
hre - OOTMM
France- isengard
england - Mordor
poland - Dol Guldur
byzantium - Angmar
hungary - Umbar
spain - Harad
venice - Rhun
saxons - Minhiriath
papal_states - Sauron
I haven't given Mordor titles yet, for various reasons.
My title for Khazad-dum (King) has earned me various wrath of Lore-addicts. However, I follow Lore too, and since my mod established Khazad-dum not under Erebor (through my readings it seemed to be an independent realm) I named it a Kingdom.
Everyone is yelling for Lord Balin, but what they don't realize is that I have intended/inserted a Lord of Moria ancillary attached to it. So Balin is King Balin of Khazad-dum, Lord of Moria... etc etc.. a system of ranks and styles that most likely would have been used if he had not died. =)