Well, the merc groups also thought they could kill Archangel, so I don't think they're too bright. xD They're probably just power-hungry and want to control Omega.
Many of my Shepards are trying to show turians that all humans aren't just a bunch of jerks who want galactic control. I wonder if that turian politician's opinion about humans changed a little when my main Shepard saved him from Thane's son.

Ironically, my main Shepard who is the most pro-turian of them all decided to side with the Illusive Man because he actually brought her back to life and is doing something about the Reaper threat. She wants an option to say "Ah yes, 'Reapers', we have dismissed that claim" to the Council in ME3, and then say something to the effect of "Just kidding, we're coming to save you" right after they look scared and abandoned. (I think the ME2 default start has the alien Council killed off. If you haven't seen the turian councillor's "Ah yes, Reapers" dialogue, then you should look it up on youtube. It's hilarious.)
My main Shepard is a Sentinel too. I think her ME1 crew would give a warning to anyone joining up with her though - do not let her drive the Mako. There's a reason why Garrus always seems to be fixing it. xD
Well, my Shepard let Garrus shoot Harkin, so she lets him have his fun. It was her payback for his flirty comments to her in the first game (and when Garrus shot him, she said "I wouldn't have shot you in the leg"). If anyone other than a turian male flirts with that Shepard, then they're in trouble.

I used the Renegade interrupt on Mouse just to see what it did, but then reloaded and didn't use it. That was just too out of character for my Shepard - beating up a guy who was just afraid of a bad guy finding out that he told on him, right in the middle of the Citadel. In her opinion, he doesn't deserve it.