http://www.axialracing.com/details.php?Id=3368&type=1
Width = 89mm
Height = 144mm
They fit any standard 40 series rim.
You are right about supply vs demand, and it would only be viable if enough people really were willing to pay a fair price for a good quality chassis. That said, the major issue so far as Mike is concerned will be time required to design the chassis in a CAD program- once it's designed & confirmed to fit without any issues, he only needs to make as many chassis as are ordered, perhaps carrying a little extra stock initially and then seeing how it goes. No need to make dozens of chassis which might not sell.
Given that people are willing to pay ~$300 for the awful looking & poor quality Kershaw Erevo and emaxx chassis, Im sure Mike could compete by selling a much better quality chassis for $200-250. If it was based on a dominatormaxx kinda design but used the tranny instead of a centerdiff ( or had options for either ), the emaxx chassis would be a hit for sure.
Erevo chassis just needs to be an alloy version of the plastic chassis essentially, but with battery trays instead of battery compartments- brace it properly & use thicker aluminium to prevent it bending, and it would make a great racing & high speed chassis..