Well from my understanding, you can set each axis to home count independantly (read that per motor).
If that doesnt work, then you could use a PLC.
i.e. Put in your ladder that when you get the Homing routine, that it jumps to a homing "Stage", or just standard ladder. As the motors hit the switch, that the PLC picks up, the PLC breaks the power to that motor. Then you "And" all the motor stopped outputs as an input, when all four have made it home, then the motors are re-enabled (pehaps you can put a timer here also), When the Re-Enable output signal activates, then it could also send this as a "Home" Signal to Mach.
The reason I say use a timer above is that, the moters will not re-enable until mach finishes sending its move off home switch signal, thus you motors will stay put, you can also "Time-out" your home switch, to fool mach into thinking that the motor have moved off the home switch, and Mach will "Zero itself there".
A DL 05 from ADC (approx. $100.00), would do the trick. If you decide to go that route, but dont want to buy the programming software, then I could program it for you, (for a modest fee).
Scott