[Edwii]

(disclaimer, I am a noob and may be talking about things beyond my level so bare with me)

So I was in the local hobby shop today, there is a used 120sr on display, so i had my first close look at one, and i look at it, and i am thinking, this thing is incredibly basic and has lots of room to work in.

How hard would it be to combine the finer points of the mcpx to the 120sr?
MCPX:
ESC
Blade grips (and head?)
(make it brushless later on)
The only thing I am unsure of is the swash, i'm pretty sure the mcpx swash wouldn't work, maybe something from an other brand?
Am I not considering something else?

Any reason i shouldn't try and make a 120cpx?
Any factors i am missing that it isnt as easy as slapping a bunch of hardware together?