[frizzen]

Since we're not rivet counting or wanting THIS exact model, it's possible to be much easier.

Before even getting into the power stick return parts, I might start by seeing how that Structo shovel can operate with something like just a dead-eye at boom tip, pulley on dipper by the bucket, pulley on boom tip, back to cable drum in house.
Maybe go a little heavier reeved so you get the 2 big sheeves by the bucket that looks like it was more common on the big machines.

It's not going to be as efficent at digging with bucket moving in a radius as the real ones pulling in an elipse, but it might not need that much engineering to work pretty well.