I was going to leave a review when you first posted this, but my brain was just fried last night.
I know what you mean about the difficulties in producing a convincing guitar part, though any instrument that gets put into the foreground like that can suffer from that issue, especially when it comes to solo writing. I think the challenge of writing around the software limitations is a good one for the brain, and it'll always be a factor since having every instrument you want on standby isn't always possible. I think your writing is good enough to stand out despite perhaps not having the little "extra spices" you'd like.
I think Shreddage is going to be a nice upgrade for your future writing, though. I remember it being very flexible from the short period of time I got to use it (probably the best guitar VSTi out there atm). I can still tell it's not a real guitar, but you'll probably find ways to make it more convincing in the future. As it stands, this will please most people. The tone of it is pretty nice. What was the amp sim you were using? Guitar Rig? I also like the use of Shreddage with SS Drums. They've always been pretty compatible, in my mind.
At 0:32, the first few notes of the guitar always remind me of "Collective Consciousness" from MGR. I think it may just be the character of the drums being similar, I dunno lol. For the rest of the song, however, it sounds much more Sakuraba-ish, like your other battle works (a quality I really enjoy). The use of the guitar to double the solo at 2:22 reminds me of the demo zirconst made for the product. Speaking of that solo, I originally didn't like the organ lead right there, but it's been growing on me as I re-listen to it. The organs throughout all add nicely to the piece.
I really like how you've written it. The parts all come together nicely, and it's very progressive with a lot of quick changes that keep it interesting. The time you spent on this one shows! Gonna have to favorite this one! :)