I'd avoid that outside wall all together. You can solve both problems (running wires and hanging the plasma) by simply building a "false" wall against it.
Stud up a new wall with your 2x4's (or even 2x6's if you want even more strength or depth) on edge instead of flat and at the usual 16" on center.
Be sure to anchor the sole plate to the floor and the top plate to the ceiling joists. You can even add additional studs to where you would like to mount the TV. The new wall will be able to hold anything you throw at it.You can then easily run the wires in the walls and hide everything.
The hardest part would be if you need to frame around any windows, accomodating any existing outlets and switches in the exisiting wall and drywall & finishing. Do you have any friends who can help you over a few refreshments?
