You can not get a trailer without brakes, if the trailer including load capacity goes over 750kg brakes are mandatory.
I have 2 possibilitys for the lpg, one is 2 small ones in front of the rear crossbrace or one in front of the cargo space, There is going to be a teak deck on top of the cargo area, hence the space under floor for the sadlle, so it will be out of site.
Our laws regarding brakes are similar. I've run with 2000 kg and no brakes... That said my rear discs are originally from the front of a 3000 kg vehicle.

