Just on my phone right now, but a couple of things:
1) similar to what Jan did, but check the size/weight of mirrorless combinations you may want. Last I checked FF lenses were still large, significantly negating a minor savings with the body
2) cropped sensor lenses are smaller/lighter
2). Ergonomics. While some like the mirrorless ergonomics, I am hearing most do not.

That said, I’d recommend taking a look at a SL2, M5 or M6 if you want to stay in Canon.

But, to save much weight over a 6D, you’ll likely need to go to a cropped sensor. Fortunately, they are better than ever.

I am not sure if you remember Juza. He was a forum member for awhile. I still occasionally check his stuff out.

Anyway, he talked awhile ago about making the switch to mirrorless:
https://www.juzaphoto.com/m_articles...&npost=&show=&

He may be back to FF, as I see articles on the A7S, 6D and 5DS

Anyway, if you need to go light, crop sensor cameras are very capable.

I’d still think about support.

Good luck.