I doubt they would be willing. They are have their hands full making all those 1:150 Japanese-prototype vehicles. But IIRC, I think their motorized bus was 1:160. I suppose it wouldn't hurt to suggest that to them.
Walthers "worked" with TomyTec to have the 1:160 scale GMC TDH 4512 produced, and Faller "worked" with TomyTec to have the 1:160 scale Mercedes Citaro produced.
I have no way of knowing how much (if anything) Walthers or Faller invested in the development of those models. However, it does show that TomyTec is willing to produce 1:160 scale models.