I would love it if LiFePO4 was a viable solution for an ebike. I use it for my portable power station and my home system, which have 2 kwh and 9 kwh of storage, respectively. The energy density is just too low to be practical. I've carried my 2kwh unit and its like 65 lbs. Each of my three 3kwh home units are literally 99 lbs. Scale that down to ebike size and I bet we are adding 10 lbs to a bike. My 35ah 21700 pack on my most recent cargo bike build... I don't even want to think about how heavy that would be in LiFePO4.
But boy I sure wish it was workable cuz I would really like to have all those extra charge cycles, and the tolerance for high state of charge.
Considering the solid state cells that are in pilot production now, and how long it took 21700's to go from this same phase to commonality as they finally are now, I bet it will be at least another five years before we are able to look past the Li-NMC 21700 cell to whatever is next.