I don't think you can do that. The CV joints go into the front main bearings, and those would be full of dirt in no time. Plus, I think they hold it together some. and the CV joints can't be free either, they can almost touch the ground when you disconnect them from the half shaft.
Honestly, from what I've done to my eagle, and what I've read, unless you do some serious converting, the car is what it is. It's a good design (full-time 4x4 even on dry pavement) and it's pretty trouble free.
If you just looking to increase your fuel mileage, then do (what they call) a stroker motor, or tune the car up, or convert the intake, or consider putting a 4.0 in her.
There are lots of things you can do to the car to get better gas mileage, but converting the drive train would be a big job - And I don't think it would yield the results you're looking for. Once you swap out the Transfer case, you're probably looking at at least one new drive shaft, then you would need to swap out the front half-shaft to get it to be a disconnect, and then there's probably more you'd have to convert to make the whole thing work together (I can't think of more right now... sorry)
The cheapest thing to do right now, is upgrade your ignition, remove some of the pollution gear (unless you're not allowed by law where you live), Then do a carb upgrade. Those three things (if you're allowed removing pollution gear) would give you a really good jump in mileage. IIRC, possibly 5-7 (or into the high 20's) increased mileage?
I don't know the actual the numbers, but it would be very notice-able.