I...I don't really see the point.
The ego/sleeve split is where the game gets most of its truly interesting philosophical concepts. Without that, you lose morphological freedom and all the gender, body-modification, and synthetic vs. organic vs. pod controversies. Without ego storage and stacks, you lose forking, continuity lose, and all the existential horror.
I'm not sure Steampunk can cover nanotech, no matter how many gears might be added. So there goes the majority of the exsurgent virus. If the nanotech comes from space and attacks a Victorian-Industrial society, how the hell does ANYBODY survive the Fall anyway? You could have a copper-tubing computer viruses and robots of some kind, I suppose, but then aren't they fighting those automatons on Earth? Do you want to go so far as magic space blimps and wooden habitats?
It sounds like you'd just be creating an entirely new system that uses some d100 mechanics. I'm not sure how it could still be called EP or satisfy that half of the group.
If you really want to mix the systems, I suggest a half-and-half approach. Make all the PC's Firewall sentinels, and have them investigate some complex X-threat lurking inside an immersive simspace MMO. The infomorph gameplay will be indistinguishable from Steampunk high-adventure so long as you don't let them hack the system. If they die in game or need to take real world action, have them sleeve into some crazy futuristic EP setting. You could really separate the two and have the infomorphs be Beta forks of themselves. Make the simulspace a pervasive storage hub for egos with no useful skills to earn a sleeve; they all chose to get their memories cut out and live in the gear-Matrix instead. These unwitting Sentinels get their Steampunk missions from patrons, which are actually their alpha forks relaying mission critical information derived from a typical EP game.