I thought about this once so I will take a stab

It would be tough

If you just added a stiff uniform carbon skin, the skin would be stiffer and would take all the load until it cracked/broke.

If you add enough carbon, to take the load, the old comptip is useless weight

A nonuniform reinforcement, basically a flexible mast that would take part of the load, would be tough to design.

If I were doing it, I would either

vacuum bag thin (2-4 oz?)glass to the outside

add an existing mast (windsurfer tip) to the inside as a sleeve. Attaching it at the metal mast joint, top of the comptip, and any hounds. This transfers bending as compression to the metal mast.

I guess what I am saying, you can do it but it will not be easy.