You don't have to use the Sachse although it is the only "ready to fit" kit I've seen, you could use any 360deg parallel twin ignition system. A basic Dyna or Newtronics/Piranha is just a points replacement system that retains the auto advance. Some systems are described "Transistor Assisted Contact" and retain the points to trigger the black box, Pazon make an expensive one and Vellemen make a very cheap kit for this costing around 15GBP.
Designs with an electronic advance would be better as the advance units on the Tornados are all old and tired by now. For this you could use a better Dyna, Boyer Bransen, Ignitech, Electrex, Pazon, Mega squirt, Lucas Rita etc.
The main problem with using any alternative system is making it fit. You'll need to make a custom sensor plate to replace the points plate and attach the rotor to the points cam shaft. Advance curves may differ but there's probably one that's suitable.
Remember with a 360Deg parallel twin you can use a wasted spark system with just one ignition amplifier and a twin output coil.
Let us know what you decide to do