Adam
The issue is that cranking an engine as big as the Maserati's V8 is that the Battery needs to deliver a lot of current (around 80Amps) . I would be loathed to use such a device as any extra surge of current could fry the ECU (I'd have to look at the circuit to what protection in in place)
To quickly start my car, I've used my Seat Ibiza diesel to charge my Maserati's Battery with the battery isolator in the off position for around five to ten minutes, this would quickly charge the battery with enough charge to start the Maserati (I've since disconnected the Seat and re-engaged the isolator). I would then run the car for around 10-15 minutes to re-charge the battery. If, after this run the battery wouldn't restart the engine again, I would trickle charge/condition the battery using my 5A CTEK charger, others are available.
I find that the 4200 would discharge the battery in around two weeks, ie the car will not properly crank over even with a healthy battery. So it's best to charge the battery continually or run the car for around an hour every two weeks.
An alternative to all of this is to have an off-grid solar system. I have a few solar panels (Around 150W) connected via a charge controller to a bank of lead-acid 'leisure' batteries. The charge controller, not only controls the charging of the batteries but also their output to the load. Therefore, this can be used to keep the car battery at a constant 12V. The charge controller has the ability to self-monitor its output current and voltage thus reducing any risk of damage to the Maserati's electrics. I've tested this method with my ZXR battery and it works a treat.
The important thing to note, is to disconnect the charger before cranking the engine!