visualchaosfx,

A keyboard hack would work for most functions......... but keyboards are set up for momentary switches.  Most of the switches you'd want on an MCP are rotaries and press on/ press off types.  While there are some "work arounds" for this, there are FAR easier and not that expensive solutions.

Look into one of the keyboard emulator cards....such as the Hagstrom KE-72.  They allow any kind of switch to be used, and each switch can be programmed with a macro of keystrokes upon "make" and on "break".  They are very nice... I have two in my pit on two different machines.

On an MCP one of the key features is having some digital readouts.  This can be done many ways but if you can't build one..... look into Phidgets TextLCD units.  These multi-line display units come with a bundled 8 digital inputs, 8 analog inputs, and 8 digital outputs.  This would allow the display of numbers along with the use of rotary encoders on the analog inputs for controlling functions.... and you'd be able to light up some LEDs too.

In the end..... an MCP you mainly build from scratch is NOT going to cost astronomically less than some of the available commercial units.  All the hardware adds up fast.  And if you time is worth anything... you have to consider that too.

A lot of "money saving" is traded for "time spent".  Electronic fabrication skills are a big plus in this hobby.  The more you can build yourself... the less this will all cost.  But it is not "cheap" by ANY stretch of the imagination.    

Hope these thoughts help.  Check out the "resources" sticky at the top of the forum.

best,

.....................john