Long story short:

No.

No mass-production 20" bike has the combo of all those qualities. The reality is that everything you need to do to make a folding bike more convenient is going to involve a compromise.

Closest you can get is probably a Bike Friday New World Tourist. Fully customizable, including internal hubs, bar height, bar type and paint job; packs well; long wheelbase; durable and rugged. You might be able to talk them into using disc brakes, if money is no object.