I just found this thread tonight. I believe the 1500 triggers could be used on other models but one question that came up was "would the box work on other models" and I'd say no. The box would be programmed to fire 3 coils in a sequence based on crank rotation and that wouldn't match the GL1000-1200 engines.
As for cheap alternatives to our C5 ignition:
GL1000 can use stock points (readily available)
GL1100 can use stock points with cam swap or drilling the cam for a bolt
GL1200 already has electronic so using automotive triggers might even work
I am working on a kit that fits GL1000, 1100, 1200, and 1500 cylinder heads using the same housing. I'll create a new post next week after we get it finalized but before we manufacture the parts. I am considering a group discount but it must be a large enough order to reduce our manufacturing costs (about 12 would do it). Food for thought anyway. Happy New Year everyone!!