I don’t know how much crowd-sourced help you’d like to have… but it would be cool if there’s a way for contributors to be able to easily access each shot at any completed stage of restoration. For example:

raw scan only
raw scan + Dr Dre color restoration
color restoration + stabilization
stabilization + rough dirt pass
rough dirt pass + fine dirt pass
fine dirt pass + final scene-to-scene color correction
etc. etc.

One-shot-at-a-time lossless downloads would prevent a whole movie from running wild on the internet, and restoration enthusiasts could learn and sharpen their skills on easily-manageable chunks. The obvious downside is the massive duplication of material when successive passes are rendered and uploaded. Some work, though, could be XML-only corrections that the end user renders on their own workstation. This would help alleviate duplicate fully-rendered version-after-versioned footage from accumulating on the project server.