I would have a go at repairing those Chabaz scales, especially as you seem to want to keep it as original as possible. I would guess they are celluloid, and the others will have to chip in on how well different adhesives stick to celluloid, but that apart it is perfectly doable. I did these the other day, I believe they are bakelite:
Attachment 320309
I know the damage doesn't extend quite as far as the pivot, but I don't think that need make a big difference. The basic idea is to use a liner, but I wanted a liner that would be invisible. So, I made the liner smaller than the profile of the scales. Also, because it was close to the pivot, I put right angles on the edges of the insert for stiffness. The liner is made from 0.3mm brass sheet. Then I drilled the insert to give an extra mechanical lock with the adhesive:
Attachment 320310Attachment 320311
Next stage was to cut into the scales so that the insert could be glued in flush:
Attachment 320312
Then the insert was glued in, and the missing section re-built with filled epoxy resin:
Attachment 320314Attachment 320313Attachment 320315Attachment 320316
I have had success gluing small sections of celluloid with CA (superglue), I'd be curious what the board says about gluing celluloid. Other than that, I think it is very doable, it took me about two hours with basic hand tools. The great thing about having the insert/liner going through the pivot is that the pivot should to some extent clamp it all together.
What say the board about gluing celluloid?