I think this is a great idea and wish you best of luck, especially if you can crack the nut on how to get many mappers helping on this. I recently ran I similar challenge, as part of a larger project to just add surfaces on the rural roads of Minnesota. If you don’t mind I’ll share my experience. First, I’ve been working on this by myself as my main OSM work for about 3-4 months. I thought I might get some engagement from others by starting a project on the wiki and announcing it on the OSMUS slack channel. Then I added a maproulette challenge as another, easier point of entry. Over the month that I had the MR challenge up (it had 1000 tasks), I got 10 tasks completed by others, while I completed 12 counties (each with 200-1500 tasks).
What do I think I’ve learned from this that you might learn from? First, I really like your tight framing of what to do, i.e. just change these tags or give a reason you couldn’t. I asked people to change the surface and potentially change highway tags (to driveways) and to fix awful geometry, so I think your challenge is clearer. Second, I think the MR interface to iD and JOSM is just too clunky for people to make 100s of fixes, so, unless you can recruit people, it will be very slow going. If there was a way to MR tasks where you could select from a menu in the MR interface (like you can with cooperative challenges) I think it would be much easier for a casual mapper to plow through a bunch of these really simple tasks.
What would I do in the future? I think something like this would be better done with the Tasking Manager where a mapper would change all the roads in a smaller (say square mile) area. I think you could map more efficiently if you can fix 10s of roads before leaving the editor and progress would be much easier to see if you’re clicking off sub areas, as opposed to individual roads.
I don’t want this to sound critical, because I’ve definitely not figured out how to do this very well, and I’d be happy to share other experiences with you if you have any questions.