What if you use a combination of zwift on AppleTV and SYSTEM X on a windows computer? Almost like described her, but “opposite”: Wahoo Systm with Zwift - #10 by knut
On the AppleTV run Zwift, with bluetooth, chose a flat route. Do virtual gearing in zwift. Run SYSTM on the windows laptop with an ANT USB dongle (from Garmin btw). Then pair via ANT with “Power” and not controllable. Now zwift controls the resistanse, but SYSTM will “follow”. Use virtual gearing. Do the full frontal/half monty in SYSTEM X.
I haven’t tried this myself, but hopefully it will work. Please let me know if anyone had any success 