Is it possible???

Only if you're willing to create your own circuitboard for it.

That is, unless you want it to have the same old layout as before, only with a whole lot of empty space between the few remaining keys.
Then you can just pull off the keycaps you don't need and place a piece of plastic with cutouts over the keyboard to hide the holes.

If what you're proposing is to take the keyboard, and remove all the keys except the ones you want to use, perhaps in a D-pad sort of array or whatnot, you simply need to gently pry the keys out with a jeweler's screwdriver (or really, many things will work) to your satisfaction.

If you are talking about taking out the keys, and building your own gamepad, good luck there. Most modern keyboards are membrane keyboards, there isn't much you can work with at all for that purpose. Older mechanical based keyboards, like IBM's Model M (LOVED those things), and I think some of Apple's older keyboards (I seem to remember a mechanical egronomic model) are that way, still, difficult thing to pull off.

I took a really old joy stick and modded it into a dpad.

If you just want a small keypad and the layout isn't the issue, you could get an external (USB/ADB) numeric keypad and assign the keys in your game or with QuicKeys.