I`ve also been thinking about the MI5 hub for a touring wheelset but found that you can get the PW cassette touring hub for around the same price online. LicktonBikes for eg.

I also like the 7sp freewheel option but it`s hard to source good quality fw in touring range ie 32 or 34 large sprocket. As for 7sp cassettes, plenty of cheap 13-34 `K` cassettes still around. Looking at the amount of metal in 7sp teeth, they must last a lot longer than 9sp.