The respected SRAM P5, five-speed hub has an acceptably narrow OLD and as wide an over-all gear range as a Shimano 7-speed (with larger jumps between the ratios, obviously). You'd need to build or source a wheel with this hub, plus the necessary shifter. With the 46 tooth chainwheel/13 tooth cog from the bike's current set-up, you'd have five ratios from ~30 gear inches to ~75 gear inches. Not spectacular, but actually pretty close to the touring ratios recomended by Velocio.

tcs