Just get a trailer.

A trailer will be more versatile, lighter, aerodynamically better, cheaper, easier to transport, and lighter than a Big Dummy. It won't have a significant weight penalty compared to four panniers and a backpack.

Also, you can probably just throw a good-sized backpack with all your stuff onto the trailer and you're done.

I'm also very confused about why you're worrying about a kg here and there, when you're apparently carrying a ton of gear. I suspect that if weight was a genuine concern, you'd start paring down your kit. It's like worrying about a dripping faucet while the sprinklers are going off.

While you should feel free to carry what you want, again it's a trade-off. More stuff = more hassle. If you want to bring the kitchen sink with you, go for it -- but don't blame your luggage system because it's inconvenient. The problem is not that panniers don't work, it's that you apparently do not want to pay the price for carrying all that stuff with you.