I'd say that if the rust is along the length of the spoke that removing it, and keeping it off, shouldn't weaken it too much. However, if there's rust at the elbow/head of the spoke...then you should definately replace it. That's where about 99% of all spoke failures happen. Having corrosion there is just going to hasten the failure. If there's rust at the threads, that needs replaced too. But just using steel wool to get rust off the length of the spoke should be OK.

However, If you're "restoring" the bike...I take that to mean you want to improve the bike's aesthetics (unless you're restoring just for functionality). If that's the case, then I'd say go ahead and replace the spokes with some that won't rust. That might mean completely re-lacing the wheel. Might be more work than you're willing to take on. Mabye new wheels are in order.

Dan