I’m sure it’s already been considered, but I’d really suggest some form of a subscription possibility for intervals.icu. The quicker you have an option for people to pay (with transaction costs for site and user that are not obscene), and clear value differentiation between free and paid, the better for your growth over time.
While you could simply make some features only available to paid users, you could also add specific services that would be paid-only (and later can bundle or modify). For example, a major pain point for many people, including me, seems to be a central place to deposit all our workouts/rides, keep them safe, and then ideally upload to other networks we want to use. I’d pay for that in a heartbeat.
Obviously, such a service would need to import from Wahoo, Garmin, Strava, and multiple sources. But then, it’d be fantastic if it would automatically make a backup copy of each ride’s FIT file for me on Dropbox or Google Drive, and then upload to Strava or Training Peaks or wherever the user says. The hassle of getting all my workouts from their source (Wahoo, Garmin, StagesBike, Zwift) into Training Peaks, and uploaded to Strava to share with friends, and trying to keep a backup copy of each workout/ride, is really a pain.
If you can import all my rides, make a backup copy, and upload to Strava or whatever, that’s worth $50 a year to me. And that’s a service you can sell to ANYONE, whether they’re an intervals.icu user or not.
A much bigger challenge (I’d guess) is duplicating the calendar, custom-workout creation, and library tools from something like TP. But those alone are worth the price of the TP Premium plan I pay for.
Just a couple of ideas. But whatever you do, please… PLEASE… keep it pretty brand-agnostic. There’s plenty of Wahoo-only users, Garmin-only users, etc. But a lot of us use multiple tools and ecosystems.