The trouble with 2 apps is that people running the new app (whichever that is) would need to pay again, which isn't really fair.
Perhaps … make a new “WorkOutLite” app that’s a fork of the current production code? Either make it free or charge the smallest possible amount. In the future, it gets the bare minimum of updates necessary to keep it on life support for the oldest devices you’re realistically able to support. New features only come when they’re trivial for you to implement.
Then WorkOutDoors can be focussed only on new features for new watches running the latest OS calling the latest APIs.
As a practical matter … I would strongly expect that those most interested in new features from WOD would also have watches with new features — and those with old or budget watches are already used to not being able to do all the nifty new things that new watches can.
And, of course, be upfront with the version split: you don’t have the developer-hours to make new features work on old watches, but you don’t want to simply lock out those with old watches. So you give them the best you can (which is, of course, amazing!) but without letting the perfect become the enemy of the good.
In the vague future, I can imagine the two versions taking on lives of their own, with the Lite version becoming more streamlined, with fewer features but more targeted to novices and those who don’t want to have to turn all the knobs and flip all the switches while the full version continues the same trajectory you’ve kept it on. But that certainly requires more time than you have today.
b&