I think this has been discussed before, but from the direction of using ERG mode to cheat.
I would really like the ability to click to switch on ERG mode and “lock in” my current wattage (a bit like cruise control in a car).
There are 3 uses for this:
if I’ve completed a workout in erg mode then once that session has finished, my wattage will vary according to the terrain. If you want to extend your warm down, it’s harder because you’ve gone from the trainer holding you steady at 140w (or whatever) to suddenly a fluctuating wattage, worse if you finish a workout uphill!
if I want an active recovery ride and want to limit my power to less than 50% FTP
in races (!!), to push you to go harder.
On point 3, I totally understand many people will NOT want this, but it should be easy to implement in a way that doesn’t distort results, or highlights it in some way.
From my limited experience, most (all?) of my ZWIFT races I’ve been pretty much riding solo whichever category I’m in and once you realise you have no chance of catching the person in front, it becomes an ITT anyway and both interest and power slack off. Being able to lock in a wattage to challenge yourself seems reasonable, provided it’s fair to others riding without ERG mode.
For 1) and 2) above I believe that there is justification alone.