It certainly does look tough. But, if you put the load as low as possible and used a pole across the handlebars and replace the seat with a pole as levers to pick it up and to make steering and controlling it easier its a pretty good idea. Even a hundred pound load would be pretty grueling on your back, or even in a simple travois. On a bike like this, you pretty much just need to keep it balanced.

Plus on a narrow trail where a two wheeled trailer would be too wide, or a rough trail that'd make riding difficult I think this would probably be easier.

It's something I've kept in the back of my head for a while; maybe I'll even cut dowels for the purpose.