I once read an article about this once. They had to actually take out a bunch of stuff in the front of the car to and also do some mods to the rear. It was one of those project articles in a sport compact type magazine. So possible yes, worth it .... I'm going to say no.
Quite a few people have done this. You remove the center differential and weld it together so that it's locked at all times. Then you remove the front axles and plug up the holes in the front diff. Then you blow your rear diff (r160) eventually and replace it with a STI diff (R180) and new axles. With a Subaru's F/R weight balance, your car is going to handle like a Mustang (ie: not well).
Oh.. and you do this on an old junker, not a new car.
i know this post is old but just to let you know that if you remove the front axles the car prolly wont move or atleast not very good. you would just burn up the center diff/viscous coupling which ever our cars have. we dont haveLSD's so power would take path of least resistance and go straight for the front diff and it would just spin and over speed the front diff because no axles are present. The only way you could do it is if you could lock/weld the center diff/coupling but if you where to remove and open the trans then you might as well remove the front diff and transfer shafts while you are in their.
I read in SCC mag MANY years ago about this, RWD WRX. But the owner was planning to use it to drift. Anyhow, even w/ a rear LSD like the GD WRX, welding the center diff is still need IIRC.
As for handling like a Mustang , doesnt the Mustang have better F/R balance than the Subaru? There are cars w/ about a 60:40 that can handle real well, like the Evo, Cobalt SS, Mini.