The main problem is that there will be a lot of wheel flop, and this will be exacerbated with the load. Might be hard to control.
BTW you'll need about 80 mm of rake to acheive that trail figure. You'll need long blades and not all bending mandrels will work.
Wheel flop is something you get used to and a wide handlebar makes it easier to control, even with a heavy front load. This bike bike will have a long wheelbase and a larger turning radius, this makes wheel flop affect steering less, right? Or did i miss some science here?
There are bikes with same steering angle but less trail. How are those forks bent?