The cap space wouldn't work and I don't see StL giving up Thomas and Kyrou for Patches and spare parts.

Aside from this trade being ridiculous anyway, Pacioretty is worth at least those 2 prospects alone. Doesn't mean STL would put them both in the trade, but it also doesn't mean Montreal would give them Pacioretty of they did.

McCarron and a 5th, sure, you can consider them spare parts. Their value is negligible. Danault and Shaw are main roster components, though STL may not need them.