That way, at least the most visible cost of union presence would be removed, and the unions could at least claim they were concerned less with socialistic greed than with worker welfare.
Just a thought ...
This is exactly right and has been coming down the pike for more than 30 years. I can remember back when my Dad was management for Coca-Cola. The drivers and line workers wanted to go union. I can remember when "management" on all levels showed up at one small bottling plant, put a closed sign on the door, took the equipment and product and left an empty building.
My education was in labor economics and the biggest problem with unions is not salary negotiation or benefits, it's that they are a 1 size fits all structure. If they were to negotiate against a bell curve where the most productive get paid more than less productive they might survive. Anything else and all will inevitably be lost for the unions.
The most productive workers can consistently make more without the union than with them, so the net effect of a union is to reduce overall productivity and that usually means death for the company.
I believe the first thing you mentioned is the most visible cost - - benefits.