Just looking at the photos, I don't see how the manual safety would be offered as an update to existing Hellcats - the polymer frame is different, you can see how it is notched for the safety tab. I would assume (but we all know what happens when you do that...) there are also attach-points and pivots molded into the polymer.
The trigger...possibly? Depends if they changed pivot points to get the new geometry, or if they only changed the moving trigger itself. Since the same Gen2 trigger is on both the manual-safe and non-manual-safe pieces, I can't see how the manual-safety polymer would be 'redesigned' to take the new trigger, but the "old" non-manual-safe polymer wouldn't. But again, when you assume...