I've been researching alternatives on the Endless Sphere forums, here, and
eBikes Discord. Everything has its pros and cons. Mid-drives have a lot of power and can handle almost any terrain or condition, but they seem to break frequently, wear down the drivetrain a lot, and are often unreliable. The QiRoll, based on 3dxl's comments, is at least very reliable. Although the 3M grip tape hack should probably be used for hills and wet conditions, that's a minor tweak compared to the epic MacGyvering I'm reading about with mid-drives. Bafangs seem to be a more reliable mid-drive brand, but cadence riding kind of sucks, IMO — it feels more like a moped than a bike.
This thread alone makes me hesitant about mid-drive solutions.
I've had front and rear hub drives in the past, but after about a year, the internal gearing overheats because of constant hill climbs. I had one Direct Drive, but that was a burden because it wasn't consistent unless I gave it constant power, anything less, and it resisted my pedaling.
For me, what's promising is 3dxl's experiences with QiRoll. So far, he's been running them on two bicycles in somewhat rigorous traffic and brutal road conditions.
The fact that it can be physically disengaged, even if it requires stopping and doing that, is a huge plus. That means I can use the bike normally whenever I want, and it's not a permanent ebike mod — a major plus because I also use my bike to keep in shape.
The other factor is weight. Mid-drives and hubs are heavy, and so are batteries. Often so heavy, I wonder how much of the ebike wattage is being used to carry the motor/battery/controller vs my own pedaling.
Jason, I assume the owner of Qiroll, has been fantastic with replying to my questions.
By the way. He said the Flex is bidirectional, but for engineering/safety measures, they couldn't make it have regen with third-party batteries. I'll quote what he said; I'm sure he won't mind:
"Flex has bidirectional function but no regenerative braking because many third-party electrical structures are not optimized for regeneration and for safety reasons, this function is not available."
The more I research and discover problems with other methods, the more likely I'll get the QiRoll Pro.