Will receive a custom, self designed, frame next week that has been fabricated to fulfill all the needs you mentioned (except the 29 inch wheels due to expedition needs). Solitude cycles are actually built by Lee Cooper Cycles in Coventry. Lee knows his stuff but is not my preference for a builder. Dave Yates is very good as is Charlie Ralph (Alves) or for road rigs Argos Racing Cycles. Its all down to budget and knowing who is really going to build your frame, whether their design ideas meet your own and how much attention to detail they are going to put in. I also looked at Dave's course and I've also dabbled in brazing the occasional bike at home. Unfortunately time constraints did not allow me to self build on this occasion so previous experience led me back to Alves Framesets.
The bikes been designed to accommodate my less than average dimensions and will allow me to cover serious mileage as an expedition rig yet also remove the touring gear and hit the woods and single track. I used Bicycle Forests design tool to sort out the design but a little knowledge is required to get the best from the program. Important measurements to consider are seat top to BB centre and seat to bars taken from a bike you are comfortable on. Then move the figures around to suit. Go to http://www.bikeforest.com/
to down load the Java Applet.
Will post some pictures of the new retrobike on completion and hope in the near future to produce rigs similar to this in the near future with my own company. I'll hit the web master when the companies ready to roll. At the end of the day we all know what makes a reliable bike, its just modern manufacturers and the marketing men that get in the way a bit. I work to exacting standards in aviation everyday and it translates into other areas of my life. I like things to work right with no fuss and have seen the failure characteristics first hand of many modern aluminum alloys and composites. You're making the best decision to use steel stay away from 7000 series alloys on anything and carbon composites unless you're willing to pay and replace the frequently.
Keep it simple