I don't think LS's recruiting based on what days you are available is a bad thing. People already have LS's based on time zone. I don't know how any of your 1st Cons counts as an exploit either, except possibly the crafting reward thing but if this is in place as is the devs have already taken it into consideration. Your 2nd con is probably unfounded, since people have different playstyles and most people would have different days they would want to do leves. With more content coming people would most likely be doing other stuff on other days.