[member="Barrien Siegfried"]
Depends on what the FO says ooc, really. Not a call I can make, but it goes over better IC and OOC to ask rather than to demand. As for who would oppose, like I said, its kinda like the Wild West. You may just have to deal with them alone or you could be up against them, their clam, and their friends. Best to set it up ooc before hand to avoid miscommunications.
[member="Niall OOC"]
It all falls down to the clans. Remember, in peacetime the Mand'alor is just a political figurehead. The power rests with the clans. Seen Braveheart? The scene where the Brits hire on the Irish mercs to fight the Scotts? They're all related and the Irish swap sides, but think along those lines. Just because they're all Mandos doesn't mean they all think alike.
Clan Vereen may side with the Republic to fight the GA, but not the OS. Meanwhile, clan Skirata will happily side with the SSC, but outright refuse to help the GR. At the same time, maybe Clan Betna is happy to help any faction as a merc for the right price while Clan Ordo is content to sit back and just be bounty hunters and ignore the galaxy as a whole.
You'll notice that not all clans are fighting right now and not all members of those clans that are fighting are present. Before all of this, the clans were split on going to war and had been for a while. It's just one of those situations where not all the clan heads were on the same side of the fence and it took a catalyst to trigger the fighting.
... TL;DR - it kinda makes more sense if you look at it like a more rough and tumble Senate, if you turn your head and squint lol