I watched your video on AA.
And I made first tries tries before you started working on that.
It was in April 2013. I used sio2bsd linux command line tool from drac030 and realized that the original OS timing does not allow for error free SIO communication via BT.
XXL has send me his xbios loader (with modified timings) and this combination worked fine.
In the meantime I was involved in other projects (Megacart 4MB) and didn't have time for Bluetooth.
One year later I decided to continue.
Regarding your solution - it was exactly my first try with AspeQt - I used the same approach, since it is pretty straightforward.
But - have you ever tried to press the "break" key while the system was loading data? You would realize that with this approach, the communication would never recover...
When powering on the ATARI, my Logic Analyzer was detecting a byte $FF on "DATA IN", before "GetStatus" command frame. This breaks that simple logic, too.
When ATARI gets stuck, because the COMPLETE byte arrives without any delay after ACK byte, the simple logic fails as well...
It is just a matter of robustness.
Until 25.10.2014 I can't explain technical details, but I will do it after ABBUC JHV.