Originally Posted by Viich

You're out of my price range, but not my window shopping.
I'm sure there are other great options as well, but one you didn't mention was the Soma Wolverine. Disc, compatible with derailleur as well as igh or fixed without chain tensioner, split seat stay should you be interested in belt drive.
Soma claims 45mm tyres with fenders (and sells some nice fenders)
You could pair that (or another compatible frame) with Rohloff, or there are a couple Sturmey-Archer options that you could consider - their 8sp disc hub (good, but not as good as the Rohloff), or the 3sp + freehub with disc brakes CS-RK3 - it can fit a 9sp cassette in addition to the 3sp IGH. I thought the 9sp shifter at your left hand and a thumb shifter either side might help you as the 3sp hub can be shifted at a stop.

Sounds like a fun bike, whether you build or spec something custom like that or go with an off the shelf similar option.