I’ve thought about this, especially having seen how cheap high end broken frames go for…and given my carbon expertise (IT WASN’T A SPOON).
If you have to entirely cut a section of tube away, I think it’s be tricky to effect a neat repair, esp with an internal cable, but surely you could create a former using expanding foam over tubing, leaving a space for the cable?
Physically joining would be tricky, I’ve thought of tapering the “good” ends of the tube, drilling holes into the taper, then putting ball bearings or similar in between layers of your repair wrap to force it into the holes, creating a physical join.
Not sure evening would risk it on a chainstay though, it’s one of the most stressed tubes on a bike (in stark contrast to a seat stay).
The Pinkster – Member
If a chainstay has been damaged I’d be concerned about wheel alignment
If you’re not confident checking this as you go, then you shouldn’t be attempting this repair IMO! I think it’d be easy to get right.