There's nothing wrong with large-wheeled folding bikes. They're obviously a bit larger than a small wheeled one when folded, but they still fit in the boot of a car. Saneagle has had this one for nearly three years and it's done thousands of miles. It still has the original motor. Nothing serious ha gone wrong with it, although we changed just about everything through about three metamorphoses. Saneagle is a big guy and the frame has stood up to a lot of abuse from off-road use and much more powerful motors.
There's a nice one that's regularly listed on Ebay over a long period, so should be sound. It has full suspension, disc brakes and a nice LCD panel that gives several levels of PAS. I'm not sure whether the Byocycle only has one level, maximum, which doesn't suit everyone. It might have three levels, so you need to check..
MOUNTAIN BIKE ELECTRIC FOLDING 2013 model | eBay
You can buy the Byocycle on Ebay as well:
Byocycle Boxer 24" Wheel Alloy Folding Electric Bike Bicycle 36v Lithium Battery | eBay