Update time! There's a costume contest on Saturday I want to enter with this kit so I'm crunching hard to get it cohesively wearable. I've redone the trim on the kama, picked the shoulder bells off the flak vest, and done a lot of clean up on the thigh bags. I'll post all of that up later, right now I just want to post up the attachment system for my knees. I'm really proud of it!
So the way I did my knees last time was with a snap in the center of the plate and the center of my kneecap, and a strap of elastic running from one end of the plate around the back of my knee and velcroing to the other side of the plate. The knee plates have always been the most annoying part of that kit, constantly falling down, snaps unsnapping, velcro coming loose. Last troop I had to staple the elastic to the plate. So it was definitely time to completely reassess attachment.
Problems identified with the snap and elastic on the plate:
-Plate is only attached to the flight suit at one point. If that point fails, the whole plate falls down.
-Visible elastic, while allowed, is something I wanted to do away with if I could, but is necessary to hold the plate flush to the knee.
-Ideally the plate should be attached at the sides, but still need help staying straight on the knee. I wanted to be able to easily pivot it upwards, more on my thigh, to be able to kneel. So it can't just snap to the center of my knee cap.
Solution I came up with:
-Place the plate itself just about an inch higher than you would think. When kneeling, if the flight suit is tailored well enough, this pulls the material of the legs up and puts the knee plate on the thigh. But when standing, gravity pulls the plate right at the knee. I can also adjust my knee plates if they're sitting uncomfortably by raising my arms instead of awkwardly picking at my knee! One piece flight suits do have their advantages

-Magnet on either side of the plate, matching magnet inside the flight suit. This would also work with snaps.
-Elastic that runs behind the knee on the inside of the flight suit, attached to the same point as the flight suit's magnet, effectively making one circle complete circle around the knee with the plate, but not visible.
-Short loop of cord epoxied to the top center half of the plate. Clip of some kind sewn to the flight suit. This holds the plate up, but gives enough flex that the plate isn't just locked straight to the flight suit.
This gives the plate three points of attachment, all of which can flex. If the magnets are pulled off in kneeling or jumping, the loop and clip holds the plate and allows me to quickly position it back to the magnets.
Loop and clip:

Internal magnets and elastic:

Knee plate positioning (ignore the one on the left sagging a bit, I've since adjusted it but not had the opportunity to get pics taken)

