It used to be that you could get freewheels for e-bikes that had 12 (and sometimes 11) tooth smallest cogs. I think they're still out there somewhere. Apparently not the highest quality but available in both 6 and 7 speeds.
Edit: something like this
DNP Epoch Freewheel: 7 Speed 11-28T Nickel Plated @ eBikeStop.com
__________________
Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"