Hmm… hadn’t thought about it that way but someone could conceivably leave the Planner blank, never select or choose a workout, and every day MB would sync with Today’s Specificity, Focus Power and XSS (low, high, peak). Then head out (or in) and do whatever you want within those guidelines with the option to color outside the lines. 
OTOH I think it might get tedious free riding MB every day indoors. I like to ride most LIT in AUTO mode watching the Session Player or Netflix or YT on the big screen. Or tackle a variety of HIT workouts in Slope mode where the only thing that really matters is watching the rainbow gauge on EBC or the Remote/Session Player.
I’ll likely rely on MB for days when I want to ride HIT or LIT outdoors. This is HUGE feature add IMO.
Those who follow my posts know I have always been a proponent of Free Ride to Focus.
MB streamlines the process and makes it easy to take advantage of this unique way to train.
Non-Garmin users driven by FOMO might want to consider picking up a used G530 (or 520Plus).
Otherwise I imagine Xert’s next project will be adding XMB and XFAI functionality to EBC.
Now that I see how it works I’ll also use MB indoors in virtual world when I want.
I don’t subscribe to Zwift but use the free 25k once a month for kicks. Turns out you can keep going past that limit on a single ride. 