First thing to do is figure out the cost of the assembly. That's enough to scare most people out of it (myself included)
It's not just the kraken you'll need, but a whole new controller, additional extruders, etc.
Azteeg X3 Pro, 3 additional stepper drivers, 3 hobbed bolts, 12 608ZZ bearings etc
Then you probably need to get simplify3d to do what you're thinking of. And I think only like 1 firmware supports 4 extruders right now.