Honestly, the best way to make it happen is to back anyway. You can always cancel your pledge before the campaign finishes. But even if we don't reach the stretch goal, I'm just a single creator, so any additional support will help me find more time to create those solo rules down the line :)
Great! I guess you have some work-in-progress for those rules. As the system is nice in its simplicity I guess it would be easier to make it truly solo playable BUT I know your standards and just "playable" will be not good enough. I would sure think that something bigger is on your mind about the possibility to enjoy your system solo.