I ride a Moulton F rolling on 1 3/8 Comet Primos (85psi) and a Phillip's 20 custom and stock Raleigh 20 that both roll on 20 inch Marathons (70 - 80 psi)... none of these has any issues on bad roads and for the Moulton it all lies in the front and rear suspension.

It makes no sense for a company to design a suspension hub when the most practical solution to making a small wheel ride like a bigger one got figured out over 50 years ago by Sir Alex Moulton.