What is your definition of "standard VEX motors"? If you mean the Mini CIM and the BAG motor, both can fit to the CIM mount interface (the Mini CIM directly mounts, and the BAG motor would have to go through a VersaPlanetary). Keep in mind swapping motors will change the output torque, so you'll have to do your own math in those regards, but it's relatively simple. If you're referring to the VEX 393 servomotors, I'm sure a custom connection could be made, but I can't see why you would want to do that.