Ralph,
The hottest plug is going to fire first. Once ignited, the charge has no use for a second colder plug. I would run some test with different heat range plugs and take tacometer reading to see which is best. Remember that the hotter 4 cycle plugs have been used in gas/glow to keep it running without a battery. Maybe a glow driver with variable current would be a good experiment. All of the dual plug heads that I have seen were used reliability, because years ago plugs weren't as durable as in recent years. I also could see using two plugs to start the flame front at two points in a large bore engine. They use two spark plugs in many large aircraft engines for this reason. Then again, it does sound like a fun project.

Dave