There'll certainly be all of the varieties of Cybernetica as pre-Imperial factions.
Though I think it's an interesting question as to how much Martian unity there would have been pre-Mars. For example, one might assume Olympus Mons was the equivalent of, say, futuristic India/China where they've seized/annexed/enlightened-the-way-to full control of the Himalayas.
Just because they hold peak significance, it doesn't mean that there wouldn't be other 'superpowers' or coalitions of forges which (if unified) could rival those geographic powers.
The reason I bring that up is, there's a possibility that the Parliament of Mars might well be a 'token' institution, or even a quasi-unofficial club (like the G8, say), rather than an official body (like the UN), or perhaps even a smaller, less encompassing body (like the EU/NATO). Or something very different again - an academic or religious institution somewhat divorced from the 'official' mortal powers of the world.
Are we certain that the Ring is pre-Imperial? (I'm sure it's Dark Age stuff.) In that instance, there's plenty of possibility that even many of the known bodies (Titan Legions, Legio Cybernetica etc) are nowhere near as monolithic as we'd easily assume.
To that end, and this was an issue I had with the 8th Edition Codex, I felt like they missed a trick by separating everything out by Forge World for their Dogma.
Rather, even just at a basic level, I think they might have been better framing the dogmas thus:Lord Dogmatic
- Glory to the Omnissiah
as Mars, rolling two Canticles & Wrath stratagem.Hyper-Rationalist
- Refusal to Yield
as Graia, D6 not to be slain, no falling back, resist psychics.Praetor Electroid
- Relentless March
as Metallica, Shoot & Advance, sound stratagem.Divine Light
- The Solar Blessing
as Lucius etc.
You get the idea. But then identify each of the titles with specific schools/factions within
the various Forge Worlds. Mars is typically Lord Dogmatic, but in peculiar times their Dogma can become out-of-step with the rest of the Adeptus Mechanicus and there's often extreme bloodshed and dataclysm before the Fabricator General accedes to the will of the other Forge Worlds (politically), or they find some way to overturn it and secure a new FG
who'll be more... pliable. Or the schism persists and their 'new' will becomes the orthodox dogma again.
It's still vague, but I'd be happier with that than the idea that 'All of Metallica acts like this'. Obviously there's room to fanon it for my own head canon, but it would have been more satisfactory to see it in print.