In the Adventist church we have our own version of scouts called Pathfinders. It's coed and all kids have the same options for activities and earning merit badges. It's worked well for us for over 50 years. We also do campouts for all members without any problems. It's a great option for kids in our church and has been very well supported throughout the decades of its existence.
that being said, I'd prefer to see the BSA and GSA remain separate, and that there be a third option/organization available that's coed. I think it's important for boys and girls to have opportunities that are intended just for them, and that it isn't some grand political or social statement to keep others out. Boys should be allowed to be boys, and girls should be allowed to be girls, especially in this day and age where gender lines are so blurry at times.
I hate seeing people sue to break into something like the BSA. Use your energy to create something new! If the GSA aren't doing enough challenging activities, talk to your local leadership about improving the program. That seems like a no-brainer to me.