Yes with Stiga they will not start unless you: 1) have the seat down, 2) engage the hand brake, 3) have it in neutral, and 4) have the cutting disk disengaged.
I'm not 100% sure what you are trying to do, so my apologies if I get your meaning wrong.
Are you planning on using the existing switches? If so, I doubt if this will work very well, because from my memory the switches on the Stiga have a very low wattage rating. I learnt from bitter experience in the past that if you overload the existing switches on these kinds of mowers by running the wiring directly from the battery, it soon cooks the switches and they begin to malfunction. Then you end up with the same problems.
Only solution is to replace the faulty electronic ignition panel, or buy switches that can take the full wattage from the battery, if such switches even exist. I guess some old fridge switches might do the trick, if you can find some that will fit.
