One major issue comes to mind. WHat benefit will be expected from this arrangement? Other than 3 decibels?
And I have no idea what that NFB plan is. The point of NFB is to help the amp correct its own distortion. WHy would you want to connect one amps output to another amps NFB line? And then why would you want to leave the second amp without its NFB? Furthermore, with two OTs in series, the output voltage will be doubled, so if you are using that output as a NFB source and feeding it back to one amp, that amp will then get twice the NFB signal it normally expects.