Some good news:
Pear is designing a new Joystick-Mouse interface named EnterMice. It will allow to connect two standard joysticks and directly a PS/2 mouse(mechanical or optical, even wireless...) without conflicts.
The Boxsoft mouse interface works very well but interferes with some program-games that expect a joystick on Control1 port. And if you want to play with a joystick on Control1 port you need to unplug the mouse from the interface, unplug the lead that go to Serial port, and then at last insert the joystick connector. If you want return to use the mouse you have to walk back that path...
Known Boxsoft owners in the world can be counted with only a hand so Zozo thought that now is the best time to modify the mouse standard....
You already know that there are some pins unused on the Control ports. On them can be connected theoretically upto thirty buttons. Ten buttons are already reserved to the joysticks 1 and 2, so still we have space to put the mouse signals there.
The only known Program-device that use that spare buttons is precisely the Boxsoft interface, that takes one for the Left mouse button. It will remain untouched, but the four directions and Fire(Right mouse button) are moved to other unused row.
Electrically it only implies the use of the K pin instead of the J one. And, about the software, we only have to modify the Mouse.xr driver if we speak of EXOS. About SymbOS, Prodatron can easily modify the mouse routine when the standard becomes firmly established.
Pear's interface will follow that new standard, so I hope all EP users will wish one. Observing their other creations it will have a high quality and affordable price.