Had exactly the same thoughts earlier this year, I wanted a bike to do 3-4 day trips fully self sufficient and capable of fairly rough off roading. I have built an On One Scandal with horizontal slotted dropouts, an Alfine 11 hub, with Stans Tubeless Rims, 100mm Reba’s up front, with a rear rack, full mudguards, a frame bag from Wildcat and a home made mounting system for a 10l dry bag from Alpkit on the handlebars. It’s now done 140 miles along the Pennine Bridleway and the Welsh Ride Thing and apart from some initial bedding in issues with the hub, it’s not missed a beat. It handles well laden as the weight is spread about the bike and hasn’t cost a fortune, about £1,300 all in. Unfortuately the frame is no longer available but I think a new version is imminent, the whole setup is waterproof and robust, I’d post photos but haven’t got a hosting site organised yet.