I have been thinking about revising my exhaust setup from stock - I like the magnaflow idea, however, what about a side exit setup coming out right in front of the rear wheel, blended into the side skirt?

 

IMO you'll be destroying the classic lines and design of the Crossfire, but it's your car, do whatever you like.

 

while the roll bar idea was GREAT this one i don't know about. i love that look on a new Mustang or a '67 Chevelle; but i dont know about the XF...

 

I used to have that on my '94 Trans Am. Gutted cat, straight pipe split in two then capped off with quad tips. All you would see is 4 chrome tips sticking out the side by about a half inch. Loud as sh*t.

 

I've had a little experience with side exit exhaust systems, since I've had them on one of my cars for almost 35 years now.
As a visual statement, it's purely a matter of taste. Personally, I feel a car needs to have a wheelbase under 100" to properly wear them. Like the 63'-82' Vettes, AC Cobra, Vipers, the AMX, and yes, the Crossfire qualifies. But they don't look bad on the last generation Mustangs either. Of course I'm speaking of side pipes, and I think you're talking about the Mustang "rocker" style. Either way, a rocker panel, side exit exhaust would be an interesting styling exercise for the Crossfire.
There's just a few things you may want to consider before committing to such a project.
1st. Are you willing to tolerate the excess noise which will only be a matter of inches from your ear drums when your window is down.
Next, a 3.2 Mercedes V6 isn't going to sound nearly as good as a V8 does, especially when you're only going to hear it from one side of the car. Splitting the Magnaflow exhaust systems exit, will definitely change it's sound.
Remember, the pre-96' Vipers used side exit exhaust systems that created a rather anemic, almost "tractor" like sound, and was the primary reason they were replaced by a conventional design. When they finally returned on the Viper SRT 10, it was only after Dodge had redesigned the entire exhaust system, and did extensive, and expensive testing and tuning to get the Vipers exhaust to sound just right.
The point I'm trying to make is, that after going to all the time and expense of fabricating the whole set up, it may end up sounding alot like a 1.6 liter "Ricer", without a great deal of expensive trial and error on your part.
One last thing, what are you going to do with the gaping tunnel in the center of your rear bumper?

 

I think of you cross them they will work out fine. It will be strange to see a hole in the rear where the exhaust would normally go. Perhaps you could create some sort of underbody rear diffuser out of it?