If your galactic war setting doesn't have mercenaries you have a shitty setting anyways.

Man, the stuff that's in canon that would mess with people's heads...

Like a sect of Inquisitors who beleves that humanity should try to make peace and work with aliens instead of fighting all of them.

Yeah, but they're still Chapters, right?
I meant, here we've got 6 Marines, all in different colours, and then they lead a group of other Marines.

But, uh... I think we shouldn't venture further down this avenue, lest we give Kerensky an aneurysm.

Yeah, they're not fun.