Sure, FEral, an excellent idea... I've been doing such repairs
for years. Most smaller blocks use rivets as axle pins, so you have to drill the heads and then drive them out. Replacement sheaves should be available from the OEM, but if not, Ronstan has a pretty good selection. Some blocks use thin sleeves between axle and sheave, some don't. They usually are reusable, and I have mostly used bolts to replace the rivets. EAch block design will require a different approach, but none are too complicated.
Larger blocks often have bolts from the get go, and this makes it easier. Anyhow, you have little to loose, so have a go at it!