An option to see custom items (such as items with CustomModelData or Enchantments) in the REI entry list. Or if this is already planned, then:
The datapack could determine what shows up in the REI List through an option inside each recipe:

Or it could be determined in the same way datapacks can use tags:

The way you do it is of course up to you (if you do decide to add it) and I'm excited to see what comes in 2.0 :)