I've recently done a bit more touring. I use an old Airbourne Carpe Diem (the alloy one) and it seems perfect for the job, even though its as old as the hills and aesthetically its not the best looking.
Things I've found
Saddle/post choice (obviously) - the racy Fisik I had was comfy for 3 or 4 hours, not so much after 8. Changed to a Charge Spoon and that's been ace. 27.2mm seatpost adds much more comfort over the 30.9 or 31.6 'standards' which might be a consideration if you're looking at cross bikes
Cable disc brakes - no issues with bleeding, pad changes are easy and powerful enough. If I were buying a new frame, I'd look to have the rear caliper mount on the chain stay rather than seat stay to make mounting guards and a rack easier. the last trip I did I bent the back wheel which had I had canti's would have been a pain in the arse. Plenty of clearance meant it didn't bother me
Standard parts - I've recently converted all the moving parts on mine to Hope - hubs, headset and BB. The reason behind this is that by buying (almost) the best, they should last me a long time and be easier to service.
Anything BB30/pressfit I'd obviously avoid. Given a choice I'd go back to square taper and a nice set of RS7's but for now, a 105 compact and hope bb do an adequate job.
Anything niche - its just a ballache to find bits for if/when they break.
lizardskin bar tape - the 3.2mm stuff is awesome. I don't like wearing gloves so this or double wrapped bars means I don't have to
I run an old steel project II fork and whilst heavy and ugly it's never bothered me and I know it shouldn't break. I'd love a carbon one, but finding a carbon disc capable fork with rack/guard mounts is nigh on impossible or silly money. There's also that nagging doubt with carbon (i've got a few carbon bikes so not anti carbon at all) that when loaded up, miles from anywhere is it more likely to break?
Tyre clearence - cross bikes will have decent clearance as will touring bikes. I run 28mm gatorskins on fairly wide H Plus Sons which are comfy and strong. Not sure they'd fit in a dedicated road frame..