Second, yes, it's been thought about. To elaborate on what tiptronic
said, the turbo engine from the CSRT4 required modifications to be made to the sheetmetal at the front of the vehicle, making it somewhat different from the standard Caliber/Patriot/Compass. There are some folks w/ Caliber R/T's that have done the work on after-market turbos, to some good results.
Third, you can't simply swap the turbo engine from a PT Turbo or an NSRT4. the electronics which run the older model engines are vastly different than those that run the MK platform vehicles. Plus, IIRC, the engine in the NSRT4 and the PT Turbo is a cast-iron block, and ours is an aluminum block. You'd be adding a couple hundred pounds extra to the front of the vehicle in engine block weight alone, not to mention ancillaries and turbo piping. Besides which, the tranny is different, and you'd need to fab up engine and tranny mounts... but, throw enough money and elbow grease at it, and you can do anything (google the PT Bruiser sometime).
More interesting, perhaps, is what's going on w/ the Mistubishi Lancer platform, which may or may not be compatible with our car. The engines are not the same between the Pat/Compass/Caliber and the Lancer, but VERY similar (they were both designed and built by GEMA for a time), perhaps similar enough that parts swapping is possible. There is a large source of aftermarket performance parts for the Lancer (did some research today - you folks w/ 4x4 may have an option for aftermarket headers yet!), and a MUCH larger community of tuners than we have. The Patriot may just be a wolf in Jeep's clothing, ripe for tuning and modification.
Likewise, I've got a hunch that the V6 engine from a newer Dodge Avenger may fit in the 'riot as well... No basis for this yet, other than shared platform and lower-end engine options between the Pat/Compass/Caliber and the Avenger. Still researching this.
Not shooting down your ideas, but yes, it's been thought about.
And one more point to make: If you drop 4x4, you drop AWD. You can't have one without the other. What we refer to as 4x4 on this forum is actually FDII AWD system. It can act as a true "4x4" system, but all said, it's a modified FDI AWD setup that is set up for lower gearing and better traction control.