I don't see why this couldn't be done, personally. However, I think it would seriously depend on the way GM went about making Z28. For example: I'm going to use the supercharged idea (DUH!
) If that car were going to be rated at, say, 550 horse', GM would surely use at least a strengthened tranny (6L90 and dual-disk 6060); beefier rear end (probably larger diameter ring and pinion, axles, and housing); larger diameter brakes (I'm sure since SS has 4-pot calipers, upgrading to 15" rotors wouldn't be out of the question); maybe wider wheels (why go BIGGER than 20-inch standards - isn't there talk of 21-inch accessories?); and probably some stiffening in the chassis (maybe heavier-duty engine and rear axle craddles and a few extra bolt-on braces). Then, there's probably going to be appearance changes too: hood, front facia, maybe rear spoiler. That's not even thinking about adding another cooling circuit for an intercooler and everything that goes with that.
To answer your question - I'd say you could do it, but would it be cost effective?... IF, GM were to make Z28 like this, I would be willing to be a paycheck that upgrading an SS to a Z28 would be more expensive than just buying a Z28 outright from the beginning. I think this is a struggle some people face and are just anxious about; the not knowing when part.
Now, if GM were to go a more traditional route, I think adding 10-20 more horse' and dropping weight would be easier than what I speculated above. Taking away from a car is a lot easier than adding to it.
I don't have any facts to support which way GM would/have/is/was going with Z28, I'm just taking a shot in the dark