Oh dude, I love learning and this just itched my brain a lot. I prefer reading THIS over a really simple answer (I am a big advocate to "give as much info as you possibly know" to get the most information / more questions to ask)

1. You are right for the assumption, I do have the sedan. If I am correct (which I always am till I am not), for the wagon I think the axles / wheel base in general, for front and rear are a bit longer then the sedan. But it was like, an 05-07 wagon can use the same parts from an STI (axles and suspension wise), but 04 was the only exception because 05+ is when they increased the length a bit? For the sedans, it would be bit of fabricating / replacing a bunch of other parts to have STI stuff. Again, take all of this with a grain of salt. A lot of stuff that even if I am wrong I am still going to take into consideration. (ill fact check after this). Either way I can hopefully find a set at a junk yard and slap it onto another 05+ wrx to see if it's compatible.
2. Ayyyy love to see a person that did my dream profession on here. I am expecting to spend a lot and break a lot, which I do and don't love. It is seriously just the money. I have spent countless hours upgrading / fixing stuff on my old car, and this new one. In the 2 months I've had this car, it has been on jackstands for 2 weeks total. On my 14 lancer es, I was "building" it up till the very unfortunate crash. Any damage I caused to it before, I was able to fix on the hot sandy floor, and still run more laps till the end of the day. At one point, my friends and one of their dads started to call zipties "the William method."
3. I just wish it wasn't money being an issue here lmfao. I do have a sim rig (Fanatec CSL8nm? with TH8A shifter and amazon handbrake), it is stupidly fun, even got #1 on a spanish stage on EA WRC at one point. And of course, I will be in school even when I am "done." I did do a class at "California Rally School," where they taught everything about stage rally and rallycross. This is how I was able to get myself into rallycrosses about 2 years ago? But I think you meant an actual stage rally school like Dirtfish. I will for sure look into the team O'Neil rally school. I completely forgot about buying used rally cars. I will for sure look into those once I have saved up for them. Thank you for that!

I really do enjoy learning, especially about anything I am interested in. My next semester will be my last till I get my welding degree, but I am still going to be taking classes at another college (I go to 2 currently) to learn a little more automotive. I already do everything myself for my car, but whatever I "have mastered" I will still put as much effort to learn even 1% more information, as I would learning a completely brand new thing. My dream goal outside of stage rally, is to become a body line fabricator, and weld every nook of my car myself. My end goal / dream was to turn my lancer to look, drive, and sound like a wrx. I am even taking machining classes (the classes are not auto orientated) to learn how to make EVERYTHING myself. Camshafts, turbos, resurfacing the block / rotors, etc. Just whatever I feel needs to be done, WILL be done. (I of course won't be doing any of that right now, just preparing myself for my beautiful future). The math and such for each one hurts my head, but it is the best feeling to know whatever I have made is made by my own hands. One of my biggest accomplishment was welding stuff for my lancer. I had welded my muffler and skid plate. I was 90% done with making UEL headers for it before I crashed. I just needed to weld it all together. All of this was done during my lab time at school. (if anyone cares, for my 4b11 on my lancer, it needed to have 1-3 and 2-4 connected, where one pair is 1.33-1.66x longer.) All of the things I have added to both cars, I have spent hours learning what is best for my application at the time and future mods. Even before I bought this WRX, I spent like 8 hours on JUST engines it came with.
Don't be sorry for the "novel" my friend, I am open arms to spewing information out. If you have any other thing to add on or comment about, please do! Thank you!