no, i actaully belive it would be quite easy...
1) get a keyboard (and potentially a controller - an old psx one will work)you don't mind hacking to bits
2) repeat this for every key:
eg - the X key.
solder the 2 terminals of the X key to 2 seperate wires. connect this wires upto the back of the SPACEBAR key on your keyboard, in a fassion that when you press the space key, the metal contact bridges the 2 wires... it's hard to explain.
OFF:
------------
------------
ON:
-----[_]----
-----[_]----
the [] is the contact on the bottom of the spacebar. it will bridge the 2 wires going to X, which will in efffect be like pressing the X button.
so finally, your system will look like this:
Code:
|------| /=====[]================| k |
| ps2 | /=====O=================| e |
| |-------[pad1]-=====X ================| y |
|------| \=====/\================| b |
\=== pad left===========| o |
\=== pad right==========| a |
\=== pad up=============| r |
\=== pad down===========| d |
good luck on getting the mouse to work tho!!