Dunno.
Since the Bodyguard armorer class hasn't been offered yet, and I've only had to get instructions for slide disassembly (to replace a broken firing pin in an early production gun), I've not been curious about the frame. I've been told it's more complicated than the M&P series, though.
I wouldn't be surprised if the Bodyguard's frame was more like the Walther PPS (than the M&P line), in that the serial number was on a trigger housing frame insert. If so, then yes, the plastic "chassis" would be a separate part. (The PPS is more complicated, and has more parts in its frame, than the Walther 99 series.)
Would the "new" plastic part without the laser be something that could be used with an older version of the gun? Dunno. Guess I'll wait until the armorer class.
Even if it was, however, I could see the company deciding not to offer it for sale as a "part" because it requires frame disassembly beyond basic field-stripping, and might be a "factory only" option for liability concern.
I've been told that S&W has been discussing whether to continue limiting parts sales for different firearms, or making some of them more available at some point, and perhaps offering instructions for their installation/replacement. Guess we'll see.