We need a microcontroller that we can plug about 35 motors into, 6 or 7 servos, and 6 or 7 sensors into. We have the motors, motor controllers and that lot. What kind of microcontroller could do all of that and be controlled by a wireless controller.
35+7+7+1 = 50
So, any microcontroller with at least 50 I/O available.
When you say microcontroller, do you mean that, or do you mean a microcontroller board
How many motors, servos and sensors did you have running concurrently at your Vex?
Do you want to go non-Vex just to increase the amount of I/O?
The Vex microcontroller is either a PIC (18F8520 ) or a Cortex (M3).
Since it might be less confusing porting code if you go with the same microcontroller that your Vex had, perhaps you would feel more comfortable with the same controller chip.
Here's how the PIC version look:
And here's how the Cortex version look:
All that aside, if you wanna control a 50 line mix of motors, servos, sensors and remote control and don't wanna use more than one controller, you need something fast, so take a look at the ChipKit 80MHz (backwards Arduino compatible) boards or some of the faster Cortex controllers.
The best way of doing something like what you want, is with distributed processing and since microcontrollers are almost as cheap as the sand inside them, you could dedicate 1, 2 or even four for the motors alone, another one for servos and yet another for sensors - this pulls a lot of the peasant work from the master controller (and make debugging and troubleshooting childs play).
Since you already have the Vex remotes (I assume), they'll be the best, or at least the cheapest