There are only 1-2 lowers on the market with FULL ambidextrous controls. Have a left side mag release, and a bolt Catch & Release on the right side. It doesn't need to be billet though, you could also try to make it lightweight like THIS
There are no light weight lowers that also have full ambi controls.
When I say FULL, most "ambi" lowers only have a right side bolt release, but only 2 others have the bolt catch function too. The best way to go about this IMHO, is where your finger would sit about the trigger have a lever that comes out of the raised portion that protects the mag release. You push the lever up and down to release or lock the bolt.
Then send one to me for proper testing
Edit: Oh and a matching upper receiver that has the single anti rotation tab built into the top for your rails.