I understand your points, but.here’s my opinion on the issue –
I no longer use Zwift but when I did I quickly decided not to export ZWO files because you lose any and all functionality assigned to SMART workouts. You are stuck with %FTP watts.
Instead I ran the Remote Player/Monitor sectioned around the Zwift screen with power only paired to Zwift. My understanding is the beta version of the Monitor supports this option as a transparent overlay. That would be ideal but I haven’t tried it.
The downside is the need to run the mobile app at the same time and any latency between phone and Internet means the Remote Monitor won’t be in sync with the Player. However, for practical purposes it doesn’t matter since you can glance at the Player if required or listen for transition beeps.
Overall it’s a simple and quick arrangement when working. 
Plus SMART intervals are supported (curvi-linear, %MPA, LTP, XSSR principal, etc.).
There is a substantial difference in riding an exported SMART workout as a ZWO versus the real thing.
https://forum.xertonline.com/t/lesson-learned-difference-between-xert-workout-and-workout-export-to-zwift/
Also note the new Auto mode in the Player controls your trainer as needed during the interval (e.g. ERG vs Resistance/Slope mode). That won’t happen with a ZWO file.
Reference: