It's not obvious to me on paper (I need to develop that), but sometimes you get into the woods and are like, wow, you can really see this one from this way, and the other way is much trickier. Since I end up with the highest bag count of any of the local hosts in my quest for purity of challenge, maybe that's the way to do it, perhaps for orange & red sharing.
Having the same tendencies as Jens (too many controls), I do think it is worthwhile skill to develop, finding those useful placements that you can double-task but that still have value of the courses that share them. Each shared point seems to really direct and limit the range of entry/exit leg possibilities. Maybe this could be used as a system for the design of courses once in a while. Identify a dozen versatile points and then use them to drive the remainder of the course design using only x more controls (set x = some low number).
Maybe, but I'm not really convinced. I'm all for sharing controls among courses, but it seems fairly rare that a shared control works well with two directions of approach. Maybe a pit or a gully could. But probably in most cases, I think that shared controls should keep the overall flow pretty similar. Likewise, it seems rare to have an advanced control that works well for a an orange course that approaches it from a different direction. What makes an orange course easier should be the presence of attackpoints, handrails, catching features, etc. -- not the greater visibility of the bag.