Here's a composite Big Hit playfield painted yellow (pics on the IPDB) I had - they also made a composite white and a plywood wood grain in the same run. This composite pf was always in a dry location and only needed Novus 2 and carnuba.
Composites tend to bubble the finished surface with moisture and will crumble/fall apart if exposed to too much moisture. Water based products are a no-no. Your playfield looks to be a challenging restore and would be curious what HSA's response would even be. Maybe re-create artwork in the bad areas but even if you do that you would need a solid, level surface underneath first.

Big Hit yellow playfield 005 (resized).JPG
Big Hit yellow playfield-composite 003 (resized).JPG

I was editing my post above when you typed this.

I didn't know they tested using two different composites - interesting.

IMO, Big Hit was the best of all the GTB baseball games produced. Fun to play.

Clearly.

The baseball sailed right over my head and I didn't even see it