Flying within the Uk and me as P1 I would handle the emergency and in terms of weather I have already had a situation where I've taken the decision to do a diversion. The other guy is a lot more experienced than me so we definately consult each other on big decisions like wise when he is P1. Its more a level cockpit environment. In terms of flying duties we approach it most of the time ( sometimes I do the lot) where P1 does the flying and nav and co pilot does the radio. The a/c insurance requires two pilots to be aboard when passengers are carried so it can be boring for the other guy if he does a flight but just sits there so thats why we share the duties like a multi crew environment.
On the trips abroad I'm sure you can legally P1/PIC from the right so that was what we where thinking of doing. Over the FIR boundary he would then P1 from the left.
Mooneyboy