If you really know how all those little parts go together then go for it. But the fact that you're asking if you should use bolts or rivets to put it back together tells me you don't know. I don't even know how to take it apart so maybe it's just my ignorance talking. Would Victorinox Service do it?

Then again, why not try it -- you're only out $20 if you can't get it back together as well as you'd like and it might turn out great. dougwalkabout's idea of reusing the same rivets is good. At least they'll be the right size.