A minimum ratio of 2:1 is fairly common, and was also the specification for the 7-speed Shimano Nexus that came on a Finnish city bike that I owned for some time, and that bike came with a 2:1 gear ratio. It would've been easier and cheaper for me to change on that bike, though, because it used a chain, if I felt my weak human legs wouldn't overtorque it. Ultimately, I used it as-is for 5 years before moving back to the USA, mostly because I moved farther from work and took the train, mostly using it for shopping/hauling in flatter places.
Someone's been locking an Onyx across from my apartment recently, and I like it! My only worries would be the belt-drive gearing, which can be expensive to replace, and the CVT hub which shouldn't be too much trouble to replace with a more conventional IGH if you have a problem down the road. In a financial pinch, you could probably convert to chain drive, where you just size the chain accordingly. I wouldn't worry about it suddenly becoming obsolete. Even 1/8" chain drive isn't too expensive in terms of cost/distance to maintain long-term.