that exact combo has been mentioned as a way to be able to mount an AOW under an AR. By hanging the AOW under a pistol, there is no shoulder stock to turn the AOW into an SBS.
Now, would the AR need to be an AOW, or would a "regular" AR pistol be enough (fixed mag for CA)? That would take some thought to figure out all the legalities.
Do you want an AOW or C&R SBS/SBR in CA?
FrontSight Training Course certificates available $25, PM for details on them and other options.
No posts of mine are to be construed as legal advice, which can only be given by a lawyer.