Neck up to 7mm and load it with 180's, 195's or 197's.
We've been over this.
We have, but this is my dedicated super duper ultra ungodly far long range rig. It's hard to see impacts and misses at a mile with the 7mm. The heavy 338 bullets are much easier to see. That's the only reason I'd even consider 33 over 28.
I would also go 7mm (28 Nosler). Necking up the existing 26 brass is a very easy step. The 28 Nosler has plenty of horse power out past 2000 yards. It's very economical to shoot (in comparison to other ELR rounds).
On impacts at a mile. I have shot a 300 Win Mag with many times out that far. You can see impacts decent when you miss or hit. I have also shot my 7mm/300 Win Mag that far with the 195 Bergers. The 7mm 195 grain bullets hit noticeably harder than the 300 WM does, and has more fps, less drop and less wind drift than the 300 WM does. So seeing impacts or misses is much easier with the 7mm. I'm running the 195's at 2990 fps, and the 28 Nosler can run them about 3050-3100 fps. So you will be gaining more speed and energy on target.
I have never necked up the 26 Nosler to 33, but I would imagine the necks would get too thin to reliably work, especially when sizing in a standard FL die set. You would certainly need a neck bushing die to size it correctly. Plus, the 33 Nosler holds about 77-80 grains