I'd say Alchemist for Comfort Zone. A nice bit of CP regen for long crafts.

That said, to be honest, these days once I get Focused Touch and Focused Synthesis the only cross-skill actions I end up using are just Careful Synthesis II and Innovation. Both of which you'll already have.

So... Yeah, I'd say whatever floats your boat in terms of things you might want to craft/tradeskills you don't mind leveling up.