So as far as I can tell, there is not a simple way to generate a custom rigify rig. I took the sample leg rig from rigify, generated the full leg rig and then edited the rig based on changes from a tut. But as far as I know I can't make rigify generate that customized rig or find a way to save it. The rigify devtools panel only saves the meta-rigs for generating custom rigs but does not save generated result.
If I wanted to use my custom leg rig in rigify I would have manually append the leg rig, delete the default rigify leg and then join my leg to rigify rig and match the bones to the character.
Is it possible to save a custom generated rig for rigify to generate without coding?