You can offer a position on the Normandy to him, that he turns it down is another matter.
Right, it never gets to the point of Alliance approval, so it's not a factor.
Miranda is in a similar position, and can even rather clearly resign at the end of ME2.
And? That doesn't mean her ties are really severed, or that she won't get roped back in.
Also there's no reason NOT to trust her when she says she's being hunted by Cerberus as well.
Sure, there is. Shepard has nothing but her word to go by at that point.
She doesn't have a checkered past, she's a wanted murderer, pirate, and so on. You presumably don't end up in Purgatory for having a small gang career
True, which provides her with some valuable life experience she can convey to young biotics after getting her life somewhat straightened out. Reformed criminals can be valuable assets. It's a stretch, but an enjoyable and contained one.
Point remains. Miranda is, essentially, a galactic liability.