The biggest reason I’m interested in subscribing to Trainer Road is because they have the FTP step test that is much less taxing than the 20 minute FTP test. I want to test often, but it’s taxing to go all in for 20 min regularly.
I know you can create your own custom workout FTP step test in Zwift (with a nice walk through via Zwift Insider: https://zwiftinsider.com/step-test/), but Zwift could easily make this one of its integrated FTP test options and do the calculations for you. More people would test their FTP more often, and they could measure improvements easier.
You could include it every 4 weeks in training plans, and advise when to do the step test vs the the 20 min version. You could even get an alert every month or so that says, “You haven’t tested your FTP lately, interested in checking in on it?” It might help with race divisions as well.