Hi napo7,
First off all congratulation for all the work you did so far and the sharing! I'd be glad to discuss with you directly (I'm French too ;-))

I'm also in the process of designing such kind of board.
I thought of using a standard Legrand derivation box (sorry for the awkward translation but I mean "boite de derivation" in plain French). This kind of box are dedicated to this kind of purpose, hide live wire that would be exposed otherwise.
I guess 3D printing is not a bad idea in essence but it's not secure; in my opinion it would melt too easily in case of electrical disorder on the 220V parts.

Other question: Why are you moving from nrf to RFM69?

Congrats again dude, you rule!

Cheers,
Marc