Probably just a dream but if I did build my own could I just wire the 100K pots to the game port  (using the right wires in the right places)  and not have any sort of controler of chips involved???
I think that's the way, but I've never done it myself.  I prefer to start with something ready-made that works, then hack from there.  You should be able to find pinouts for such a thing in the Controls section here.
You might want to look into making a Twisty-Grip.  Dunno where you can get plans nowadays, but you might find some somewhere.  If you get a chance to buy a real Star Wars yoke (or Turbo Sub or STUN Runner), go for it!  You can't get a more solid controller, almost all metal, well worth the money, and instantly adds 1,000,000 cool points to your cabinet!  
