I must admit I've had similar thoughts about the feasibility of combining bits and pieces of prohibs with non-prohibs, in order to produce a legally registerable new type that retains at least some of the characteristics of the parent firearms. Sorta reminds me of the South Park episode where the boys try to breed an elephant with a pot-bellied pig.
The ONLY one that keeps coming to mind would be a bolt-action FN/FAL, built around a new upper receiver. There are several specially-built, competition, bolt-action FNs in Canada, so the type should be legal & non-restricted if the receiver could be built and a sample submitted to the RCMP for evaluation. You would need a supply of top-end parts, though, which would be tricky to get until the type was approved. Easiest way to do up a prototype would be to take a FN/FAL prohib, and strip everything off the upper receiver, and repopulate the essential parts onto the new, "bolt-action", upper, then submit for approval (modification of the bolt carrier would be necessary as well).
It would be an interesting project, if I could get access to one of the competition bolt-FNs for some measurements and photos. I know at least one is in a board-member's hands, but I don't recall who.