I've never heard of a "live faceplate" -- but there is something that can get you there: a live center which has the same screw threads as the lathe drive shaft. The most common use for them is to help keep a bowl centered when you're "turning it round" onto a vacuum chuck. There's no reason you couldn't put a faceplate onto it where they expect you to put the scroll chuck.I didn't know if they sold something like a faceplate but on a bearing so you could put it in your tailstock and be able to use it when the lathe is spinning to add support?
I forgot what kind of lathe you have, if it's got a 1" x 8tpi drive spindle you could use the one that PennState sells -- LINK I don't remember who makes the one for larger drive shafts, perhaps Oneway.