LIES! Benchmade and various jewelers have used some pretty darn nice looking full stainless 'Damascus' steels in the past. Wont rust any quicker than any regular stainless steel and if you wear out any steel space-bar you prolly need to work on those anger issues.
Any High carbon steel, or steel with a high carbon component will have worse corrosive resistance than good stainless steel. There are reasons for Damascus steel, but I don't think it'd be good here. What we want is two stainless steels that are folded in a similar fashion (and therefore expensive). Keep in mind that this would be in a somewhat corrosive environment for almost all it's life, especially compared to the usual usage pattern for a Damascus knife. I mean, who would want a Damascus dive knife?
When you say "composites" I think "carbon fiber", which I would totally buy.
Carbon fiber is a composite, but composite really means "made up of multiple materials", we could have an extruded brass matrix with epoxy in it, and it'd be a composite as well. Check this picture of a Steel / Copper / Steel (Sandvik 14c28N copper D2) composite blade:http://www.manventureoutpost.com/product_images/out/main/kerspic1660cb.jpg
I'd love to see that on a spacebar, though the copper bit would war/corrode faster, if it were in between the steel layers where you don't hit it with a finger, I imagine it'd be fine.