Phillip
There are advantages to starting on one ignition. The engine on one ignition has only one plug fire in the cylinder and because of this the burn very slightly reduces the pressure point...this will make it start better. We notice this slight change when we do a MAG check at 4000 RPM to see that they are both working in that when you switch one off it drops some RPM. I favor starting on one myself.
In regards to putting on 2 new modules. Sure they are great, no problem to do that to get the start delay. At the same time it would be a good idea to buy and install the newer flywheel plate also. The plate has longer trigger bars on it, this is what gives the different start timing on the newer engines. You will have the same running timing. To be clear, the old one you have is 4 degrees BTDC start and 26 degrees BTDC running. The newer plate will give you 3 degrees ATDC, after top dead centre, and the running timing remains the same at 26 BTDC.
This gets you the full advantage of the soft start system. The details are all in the Service Information Rotax released some time ago.
Cheers