Here's my solution- lace this Puch moped hub into my 26" rim using the same 12ga spokes from the 26" wheel.
Should be sufficiently strong for my 79cc build. Already has a BMX freewheel on the bicycle chain side, a bolt-on chainring on the other side that fits a #40 chain fine, and an internal drum brake.
$24 plus shipping on ebay.
You do have to spread the rear frame some to fit the hub width.
Spare parts are available everywhere for the brake and gears.