I was toying with a longbike for carrying Ojnr to nursery – it would put his weight infront of the rear axle and maintain the ability to carry panniers.
I don't have pictures to hand, but in the end I bought a cheap tandem off Ebay, removed the stokers saddle and pedals, and mounted a second rack above the rear top tube. Ojnr's child seat goes on that, and the standard rear rack has panniers perminantly mounted. If I want to carry bigger loads there's room for 4 panniers (without child) on the two racks. As a bonus, I'll be able to convert it back to a tandem when he's big enough to pedal…
It's obviously not quite as adaptable for large, awkward loads as a Yuba, but suits me perfectly.
Total cost: £200 for the bike plus another £100 for the rack and childseat.
🙂