As to the idea of the ti goat bug bivy --- it would be very helpful if you could borrow something like that first and try it out. I have a lightweight bivy, not water proof but water resistant, with some bug mesh on top. I generally find bivy's of any sort to be a restrictive PITA. I also have experience with a couple variants of bug net tent, and these tend to be really small inside. In all of these cases, a person can feel really restricted. This works for some people, but others (including me) like a larger bug-free enclosed space.

As to the Gatewood Cape --- I don't recommend it for someone as tall as you, unless you're happy sleeping every minute of the night curled up in a ball like a dog in your pet bed. I.e., you will definitely be too long (tall) to sleep anywhere close to stretched out without either or both of the head and foot end of your sleeping bag pushing up against the inside of the tarp fabric and getting wet from condensation. I'm 5'10" (at the tallest moment of the day), and I have trouble with this sometimes in my Gatewood cape, particularly with a thicker inflatable pad. It's also not that great as a poncho.

It IS a great piece of kit for specific uses. Day hikes when I'm required to have rain gear and emergency shelter --- but don't expect to need either one. Relatively short backpacking trips where I don't expect much rain --- great way to save weight in that situation, but sort of ironic that it's best in those situations where I have to rarely if ever use it ...

I took it on a hike in England as a way to take a mid-day break for my wife and I in rainy conditions; but we never set it up that way, and again, it wasn't really optimal as a poncho.
If weather is worse than I planned for, I'll do okay with it, but for me it's not a comfortable choice when I'm out for multiple days and it's pretty wet.