I totally agree.
My 400 5.6 lens when calibrated with AFMA to my 5D III is awesome. It is an old lens, but it is relatively small, light, and it also travels well. Not that expensive either. Don't rule it out for lack of is. I love my new 300 2.8 II also, but for your restrictions, do consider the 400 5.6.
If you are unsure, try to rent one before you buy, or see if one of your buddies can loan you one.
I've heard good reports of the 400 DO in practical use - as opposed to the reviews......I would check that out, too, though I can say that the 400 f/5.6 is a great lens if you can get used to the lack of IS. Many of my best photos were taken during the 4 years I owned this lens. The 300 f/2.8 II IS + 1.4x III and 2xIII is what I upgraded to and other than the cost, size, and weight, I can recommend it without reservation.
Also, your post scared me a bit as "going native" means going without clothes in American slang