Not exactly what you are looking for - but we did run 4 toughbox nano's last year with mecanum's on the AM14U. We used 8 inch mecanum wheels.
It looks like the gear ratios for the nano and mini are about the same so you should be fine there, and we ran one CIM per corner like it sounds like you want to do.
We had to add some gearbox mounting holes and bearing holes in the chassis at one end, because we cut ours to a non-standard length.
We understand the limited budget
