i got to looking at the geometry of the radwagon and it looks like the wheels are not as proprietarily sized like once thought
it looks like they may be using standard 20 inch rims i wont know until i get mine in november and i do some fitment testing.
i suspect this because the stand over hight is very close to the wheel size and i think removing the rear fender may allow 24 or even 20 inch tires to be used.
i am thinking of replacing the rear wheel with a direct drive hub for regen and a 20 inch rim to use a standard bmx or child sized bike wheel and then using a mid drive or even a motor connected to a sprocket used for gas bikes that connects to the disk brake mount for power.
i do scrap metal recycling and pull an appliance dolly and go to yard sales and have to pull heavy loads and go up steep hils and the power and regen would be nice.
i hear you saying "there are no radwagon 4 on the road yet" actually there are just starting to be radwagon 4s from early orders being delivered now and some reviewers for youtube and ebr site that got theirs early for reviews who want to probably do the same mods and can be guinea pigs for testing different size wheels.
maybe even someone can tell me if it can handle a full fat tire seeing that it looks like the hub is a rebranded bafang g60 750 watt motor witch is a fat bike motor.