I've never read the 4000 manual but I think I read on the Akai website you can control external midi devises via the q-links
Unique to the MPC4000 are the six Q-Link controls that can be assigned to a wealth of parameters for real-time control in a live performance.
Q1-Q4 are rotary controls which can be assigned to anything - filter cutoff, resonance, effects depth, amplitude, panning, pitch, even things like LFO speed and depth, envelope times and more including a variety of different effects parameters. Q-links may be assigned to several different destinations or to single programs.
Q-Links 5 and 6 are sliders. Again these can be assigned to a multitide of parameters but can also be used for switching between different samples assigned to a pad to emulate open and closed hi-hat, open and closed triangle, etc..
Each of the Q-Link controls may be individually enabled and disabled - again, all in real-time. Furthermore, it is possible to record the movements of these controls to a sequence so that the effect can be replayed time and time again. The MPC4000's extensive sequence editing functions means that your performances can be edited with detail and accuracy to create the perfect performance. And, of course, once recorded, the Q-Link controls are freed up and can be assigned to other parameters for other real-time perfomance possibilities - the mind boggles!
Combine these with the instrument's other performance features and it is likely that we could claim that the MPC4000 is possibly the most powerful, most playable sampling workstation ever....
But we're too modest for that!
It doesn't say anything about your FX rack but I would bet you could probably get some CC action outta the 4000