Alright, so, three things to know about the combat in Dougram:
1) Combat is somewhat more 'realistic', which largely means things are a bit more subdued, not that mechs are just walking tanks. Unlike Battletech (which directly lifted several designs for Dougram) Combat Armors rarely had a billion and one weapons optimized for different ranges, with a typical loadout being something like a wrist or hand carried liner gun and a shoulder mounted missile launcher. They also were agile enough to run and jump without the assistance of integrated rocketry. (Which I think actually makes it somewhat more realistic than battletech. Why use walkers if they're just going to move like tanks, after all?). And notably, when a mech went down, it would rarely end in a big explosion for no reason. They tended to just collapse.
2) Combined arms is a focus. In the show, wheeled tank destroyers and helicopter gunships (actual MBTs and Combat Jets were never deployed to Deloyer for whatever reason) are taken seriously as threats, even if not quite as much as mechs themselves. The standard enemy team would consist of Three Roundfacers and a NotCobra Gunship, the latter of which is usually portrayed as an actual problem, and not just something dealt with in half a second. Most battles have infantry involved somewhere, and a good chunk of Crinn's (Dougram's pilot) teammates have multiple mech kills to their name even thought they mostly fight on foot or with weapons mounted to trucks and stuff. Half of a team of Elite Federal pilots died because the rebels were able to catch them in massive crossfire with an ambush.
3) The role of mech pilots is deemphasized. I think you can count the number of named pilots in this series on your hands. The only one of them to be featured in more than a handful of episodes is Crinn himself. Technically more realistic, but a bit frustrating to work with here.
The Deloyer Liberation Army itself seems inspired by various anti-colonial armed groups during the Cold War, such as the Vietcong. However, in the series itself, their principal backer wasn't ideologically driven, but rivals of the Earth Federation's top nation looking to gain political power for themselves. This won't be the case here (Hi BAHRAM, Mars Zeon, and Vers!) but I put in PLANTS as a potential ally since they seemed to fit the role best.
Compared to the average mech in the series, Dougram isn't really that much more powerful. It's main advantage lies in being specialized in the terrain of Deloyer (or this case Mars) itself. In the series, there was also a thing about Deloyer passing through a nebula that caused interference with electronics and Dougram being adapted to that, but we should probably just say Minovsky particles here and call it a day.
The single offensive thing it has that most Combat Armors don't is a shoulder mounted Linear Cannon strong enough to one shot other Combat armors. Crinn's friends also got some experimental gear in the form of personal Energy weapons called E-Guns, one of which was big enough to be used as an anti-mech weapon.
If I were representing Dougram as an Orbital Frame I'd probably only put it as a Gen II at most, probably only leaning towards a Gen I.
Compared to the average mech in the series, Dougram isn't really that much more powerful. It's main advantage lies in being specialized in the terrain of Deloyer (or this case Mars) itself. In the series, there was also a thing about Deloyer passing through a nebula that caused interference with electronics and Dougram being adapted to that, but we should probably just say Minovsky particles here and call it a day.
The single offensive thing it has that most Combat Armors don't is a shoulder mounted Linear Cannon strong enough to one shot other Combat armors. Crinn's friends also got some experimental gear in the form of personal Energy weapons called E-Guns, one of which was big enough to be used as an anti-mech weapon.
If I were representing Dougram as an Orbital Frame I'd probably only put it as a Gen II at most, probably only leaning towards a Gen I.
For the rest of the Liberation Army, there are two main periods. The second is after an enemy base mutinied and defected, trigging a snowball effect where local enemy military forces would switch sizes, giving them a fairly sizable military contingent. I was leaning towards this taking place before that, but if Shrike would prefer a more conventional force for the FMLA, that's an option.
For the first two thirds of the series, the Liberation Army operated on a semi-decenteralized cell based structure mainly using conventional guerilla forces. The Fang of the Sun (Dougram's unit) was one of these. Another was that of J. Locke, a man who can best be described as Eyepatch Che Guevara in space. His team utilized a number of light wheeled combat vehicles fitted with missile launchers, and they were actually considered a serious threat on the battlefield. (Basically, imagine if that one desert resistance group from SEED had stuck around and was allowed to accomplish things) Another key member of the army would be Jackie Zaltsev, a skilled Federation tactician who defects to the rebels after being imprisoner by Von Stein. (feel free to have him start on whoever's side).
The Liberation Army also had a scheme to mass produce Combat Armors in Bonar, a city notable for having a car culture, including factories, I think. However, this gets a bit confusing. It's initially indicated that the plan is to mass produce Dougram itself, However, the Federation forces move in on the area, and the plan has to temporarily be shelved. When they finally do build their own models and they show up as cavalry one episode, that's where the weirdness starts.
A few episodes ago, a new Federation model showed up, a big chunky boi called the ironfoot. Pretty standard enemy of the week stuff, and they pull back without losing one. A couple episodes later, as I've mentioned, the base the Ironfoots (Ironfeet?) were operating from defect, giving the rebels their first Combat Armors outside of Dougram.
Now, this all seems normal, until the next big battle takes place, and the Combat Armors the Liberation Army was making itself shows up. And every single one of them are Ironfoots, despite the fact that the Federation army just introduced them. The Federation army actually never uses Ironfoots again in combat, for no adequately explained reason in universe, while the rebels in most case use nothing but them, even though they're clearly shown to have acquired other models in non-combat scenes. The out of universe reason is obviously that the animators wanted the sides to be fielding different models of mech so it wouldn't get too confusing, and were too lazy to design an MP Dougram version. I'd probably just go with making up a Dougram MP, or saying that for whatever reason, the Ironfoot IS the MP version, to keep things simpler.
Overall, since starting with only a single very okay OF is probably not practical, I'd suggest a force starting with a few defecting Mobile Weapons, but a deceptively small number of them, but a conventional force surprisingly capable in guerilla combat.
Now, if I had bring in stuff from other series to give the Free Mars Liberation Army more of a fighting chance, there are a couple of characters from Gundam SEED Destiny Astray that would fit the bill.
Edward 'Ed the Ripper' Harrelson from the United States of South America would join his home country against the Earth Alliance for generally just being evil bastards. He famously piloted the
Sword Calamity. I think you could probably adapt him to defecting to Mars. A comrade and lover of his,
Jane Houston, would also later defect. She was noted as a skilled underwater Ace, and piloted a Mobile Suit designed for that role, which probably isn't yet that useful on Mars. But Ed did bring a
Raider Full Spec with him when he defected, so that's a Suit she could plausibly use.
Some MAHQ links for FMLA equipment:
Dougram
Ironfoot
Roundfacer
Blockhead
Native Dancer