Jeff,
Long (really long) scarf joints have been used for ages, to replace damaged wood with new, and the result can be as good as new. Likewise a new mast can be made of many pieces of shorter wood.
Uniformity in the material is important, especially about the partners! Lumps of epoxy bog, or massive glass replacing wood fibre, won't help the mast - it wants to flex smoothly, or break at a discontinuity.
SeaBlossom's nicked-up timber mast can be repaired. A little 'mast money' spent consulting with a sparmaker to plan the job would be reassuring and well worth it.
I'd suggest restoring the wooden spar first. After doing a careful job on the timber repair, you can add insurance with unidirectional fibre reinforcement, gradually thinning it above and below the partners. (Glass, not carbon. Last layer double-bias or woven, not uni.) It's not a difficult process.
Cheers,
Kurt
PS - Since carbon was just mentioned in the post above, I'll clarify.
Proper carbon masts are great. Carbon to reinforce timber is tricky, because it's so much stiffer. Too much carbon concentrates stress in the adjacent wood; too little and the carbon may fail when the wood flexes, over-stressing and breaking the timber at that point. Glass is more like wood, so it avoids such extremes.