Thoughts-
- if you are doing 25mi per day up to 40 with 2-3 days rest between, then there is no need worrying about a steel rack being field repairable. The odds of a rack failing with that expected use is basically 0. 25 to 40mi with 2-3 days off between on some stops for 1-2 weeks means 90-250mi ridden and no rack should break in that time.
For many parts of the US, it's be easier to just buy a new rack wherever you are than find someone to weld the broken rack.
- many panniers have loops to connect rear lights. Those loops will place the lights at the rear of the bike and unobstructed. Always been a great place for me to hang a light(left rear pannier or on rear rack).
- maybe solar panels have improved since I last looked(I assume they have since its been a couple years), but perhaps just the battery pack is needed? You will presumably have a lot of time in camp/restaurants based on your expected ride time, so just plug the power bank into an outlet and call it good.