Well, this is incredibly easy, as I don't know anything about electronics
I have a dual X-Arcade stick (but it would be even better with a Tank Stick to add mouse support).
1) I will sacrifice 2 Amiga pads and connect each microswitch (simple "on off" mechanism) to each direction / button on the PCB. I will also map the "up" direction to one button, which will make it easier to jump in platformers games. I may also use one more button for the autofire feature which is built into my pad.
2) I would also like to add a Lyra 2 to my A1200, which will enable me to get PS2 keyboard signals. Then I need to find an adapter or use a keyboard matrix to get the signals for keys frequently used in games. (like "shift" for pinball games ; F1 F2 ; space, enter, tab etc.) and then connect them to the relevant joystick buttons.
(on the X-Arcade dual stick there are 8 buttons per player + start for each player + 2 flips on the sides for flippers).
Well, I'm pretty sure it can be done, but I'm open to any piece of advice / suggestion. Especially, how to do it properly and in a clean way. (3 cables will have to be used to connect the X-A to the Amiga)