Expansion Galore

I have been racking my brain over how I will control a normal 3d printer while adding 4 more steppers(for an additional process) and a couple more servos.

Here is what I came up with so far:

Arduino 2560 Mega with a RAMPS 1.4 connected via I2C to a Arduino Uno with two Adafruit Driver Sheilds

IS THIS POSSIBLE?

If not, what do you suggest?

Additionally, how well does I2C work between two boards when I need to essentially control all of the motors one after the other?

Lastly, how complicated is this going to make my code if I start out with standard Marlin for 3d Printing?

Thank you SO much for all of y'alls help.

Are there not enough unused pins to do it with the mega? I don't think RAMPS uses every pin... There may be enough?

I am unsure about this.

Please expand on what you believe is possible.

What 3D program are you currently using on the Mega?

Why not use a second Mega with another RAMPs board as you are already familiar with that?
If the Adafruit Driver Shields do not use specialized stepper driver chips (such as the A4988 or DRV8825) I would not use them.

Driving 7 or 8 steppers with one 16MHz Arduino may be difficult if you need high step speeds.

You have not told us what the "additional process" is or how closely it must be synchronized with the 3D printer. If you need close synchronization that will need careful planning.

...R