I am not the dog owner , the OP is. my concept is Making The CF C, more utilitarian..

It is smaller than the Burly Flatbed.

they have rear edge rollers like the stock Brommy Rack rollers,
may replace the barely big enough, to not drag on a hard surface wheels
with a rack set of EZ wheels. to easily roll the trailer on edge , as intended .
folding the cable stayed wheels In... and the tongue down It stows in a small space.