Starting with a MTB seems to be the logical idea to me. But after reading PastorBob above, I guess even that's a bit sketchy, for front-drive.

The only Ebike I've actually ridden is this rear-drive fat bike, which my brother in law bought for commuting in Seattle. It's pretty cool, but also really heavy. 60 lbs

From a physics standpoint, it makes sense that a sturdy rear triangle beats any fork for holding up to the extra weight and torque of an electric drive. Not as cool as the $5000 examples above, but the same principle in terms of construction. ($1500)