I know, I know, there isn't still a game that takes advantage of the three possible fire buttons per joystick that an EnterMice can provide.
But somebody must start walking, and the first thing is to have a three buttons joystick that can be connected to it.
The principal problem when trying to implement three buttons on a standard joystick (Kempston, Amiga, Atari) is that the cable and connector don't have the nine pins populated. Normally the fifth pin or more are hollow, without the little round female connector inside the hole.
So if someone wants to fully adapt a Joystick to the ports of the EnterMice he has to change the cable and connector that come with the joystick with a nine lead cable and a big and ugly D-sub 9 pin connector with two long bolts at the sides. You can remove the two bolts, but the connector will remain ugly and large compared with the original.
A solution can be to buy a joystick extension lead cable like
this, cut the male side(the pins are male) and weld it to the joystick. This have its cost...
There are joysticks with more than two buttons, some of them repeated, for left handled users, that can be adapted to three buttons by this method.