I've considered cameras like the ProPaq and other homemade alternatives for quite a while. The very expensive Alpa is basically the same idea only very well done. But for the money, I think 4x5 and Readyloads is a lot better use of your time for not much more hassle. On the low end a Crown Graphic - or on the high side a Technika - and you can really shoot. Otherwise, if you just want a good roll film 120 camera, pick up one of the great bargain Mamiyas or Hasselblads that are flooding the market.
Personally, I don't see the point of roll film anymore, digital is that good. If you're going to hassle with film, use a sheet.