Since this thread has gone all quiet for now....
Here is something to get you sending all kind of flames my way.
But, but, but....
This is just exploring an idea that started with some mechanic suggesting welding as a solution......
Along the lines of swapping in a pressure plate + clutch: what would happen if a manual (spring-loaded) clutch disc (with the correct center spline dimensions) was inserted and welded to the outer steel ring that comes off the busted up rubber donut assembly. This assembly would then be bolted to the starter flywheel etc.
A competent machine shop should be able to get sufficient precision into the process of putting together the revised assembly at reasonable cost.
The only question then would be which clutch disc would do the trick.
Just a (crazy) idea... any comments?