I agree with the post earlier. I think it would be more work to have someone up there that wasn't trained on the aircraft. This is not being macho or thinking I am the greatest but there is going to be enough stress going on without having to worry about jo blow next to me.
If you want to get technical, when I declare the emergancy, I own everything...any airport, any airspace (minus P-56) etc. If I had to, I would say I am declaring an emergancy and returning/diverting to xxx, need the trucks and THATS IT!!! At that point if I needed to I don't have to say another word. If I get to busy then tough. Aviate, navigate, COMMUNICATE. The last time I checked, that came last. As far as checklists, once again, if you want to get technical the airplane will tell me if I forget anything MAJOR (i.e. gear flaps). If I forget to ARM the reversers...ohh well, the airplane was certified with just the brakes. If I forget the landing data...oh well, I will land it at 146kts which is our highest VRef+5. Everything else is secondary.
I am not really concerned with terrorist or CASS or anything, I just don't want to spend the time explaining how to work radios and tune this and do that. After completing ground school and CPT on the airplane, it was still a goat screw the first time we got in the sim...I couldn't imagine how it would be with someone just flying cessnas. I think it would put more stress on me when, as stated before, we (FO's) are actually trained on the airplane and could land it just fine single pilot.
Hey, what about that flight where the CA or FO lost it and went crazy. Did the other pilot start asking the cabin if someone could help him...nooooo he did it himself, as I am sure most of you would too!