I am planning a multicity itinerary on United and Lufthansa as follows (A-->B-->C-->B-->A), and am trying to figure out how to reduce the fare. There are reasonable business class fares for this itinerary, but they require me to fly from C-->B (third leg) too early in the morning for my meetings that day. But if I book the later flight from C-->B that works with my schedule, the fare jumps up nearly $2000 because the later flight (on a partner airline) is forced into J class (rather than D). I tried to use the online booking engine to force the C-->B flight into coach, but that doesn't seem possible for some reason. The one-way coach fare from C-->B is about $1000 for the flight I want to take.

Here's my question. I would like to book the multicity itinerary at the lower rate with the C-->B flight at the earlier time (which I cannot take) and book a 1 way fare from C-->B at thetime. This would end up saving me more than $1000. What happens to the rest of my itinerary if I "miss" my scheduled flight from C-->B? I know that normally United would cancel the final leg, but what if I call at the last minute to say that I overslept or something and can't make the third leg? Can I still keep my final return flight (B-->A) if I get myself from C-->B on a separate itinerary?

Does it matter if the first and last legs are on United, while the middle 2 are on Lufthansa?