Yeah, If I had the money, I'd make my WRX be able to rape that Stage II STI on every surface while carrying 5 people. I'd also drive it every day and basically make it the perfect weekend warrior year round shuttle rocket.
Just do it in your OBS. STI swap into a lighter car you're golden. There is a kid from Mass. with a 98 OBS with a complete STI swap, down to the wheels, it looks sick.
I would if my car had less rust. Once I get more skill in welding/metal fab, I might go to work on fixing it, but as it sits, my OBS is not a good starting point. I could see it as a parts car or normal person daily driver, but it's not the right car for an STI swap. If I ever get large amounts of money though, I'd have the rallied out WRX wagon and a beater OBS with a WRX swap.
That 06-07 WRX Wagon is exactly what my dream Subie would start like. It'd end a hell of a lot like that too, just slightly more rally looking. (Very small lift and more skidplate showing...that and the bigger, much louder exhaust...)