The Skarper e-bike conversion kit has been recently announced
https://www.sigmasports.com/item/Skarper/eBike-Drive-System/14PRJ#description. It's an interesting approach in that it's easily removable if not needed. It doesn't appear, however, to be compatible with a Rohloff hub as, even if a Rohloff-compatible modified brake rotor becomes available, it would clash with the Rohloff gear shift mechanism.
