Implemented in the development version.
Apart from the Convert To Rigify button, there are now two new buttons: Create Metarig and Rigify Metarig. So you can create the metarig from the DAZ rig, do whatever you want with it, and then convert the modified metarig to rigify.
It is important that you don’t delete the original rig after creating the metarig. It still contains a lot of info (like drivers) that is needed in the second step.
I’m not using rigify myself, so I haven’t tested making any advanced changes to the metarig. But if you press the two new buttons in order, you get the same result as before. If you modify the metarig, things may or may not work