You have touched on some points that I have addressed in other threads. I believe we should pay more attention to KimJ because she is a key to many things. The fact that she has NEVER been seen in an alliance talk with anyone, even in Survivor Insider (based on what I have read) says a lot to me. I cannot believe she would never have any such talks. MB ALWAYS hides a bit of the alliances because otherwise things are too predictable.I have my own reading of KimJ being the one that would be thrown out if they had lost IC in E4. I believe that her conversation with Ethan was a result of the fact that LET are all aligned with KimJ (probably with the sub-alliances of LT and EK). This is supported by the Survivor Insider clip of Kelly and Clarence talking about voting off Lex but not being sure that KimJ would go along. Of course, Kelly may be in an alliance with Ethan or others and may have been blowing smoke up Clarence's butt.
Back to my basic point. I think that KimJ was told by LET that if they lost in E4 they would HAVE to throw her overboard because if they go down 6-4 at the merge the whole tribe is lost (they had no idea how divided Samburu was at that point). She understands this reality and reluctantly agrees (what can she really do). But I bet the promise was made that if they got close enough to the merge, she would be safe and back in the alliance full steam ahead. Of course this is much speculation, but I think I have some evidence as noted above.
So let's track your thinking a bit. Does KimJ have an incentive to go over to Frank and Teresa. Well, if I am right then NO, she is part of a strong alliance and would be a fool to give that up. But what if I am wrong. KimJ was clearly vulnerable pre-merge only because of physical weakness. After a merge this would be irrelevant so again I take nothing from the fact that she would have been tossed over pre-merge from how she would be treated by her old tribe mates post-merge.
If she does go in with Frank and Teresa--she pretty much has made her choice and will have no other allies. She knows that any GXAers that may be left post-merge will be happy to join anyone that is trying to take out her new alliance partners. So once a merge took place--there is a great chance that Ethan -- if he is left -- will join everyone else to vote off Frank and Teresa and then probably KimJ -- then the rest of the GXAers would be taken care of.
No--her best bet is to wait for the merge and hope that whatever strategy she was relying on before (e.g., an alliance with Ethan or an alliance with Kelly and Clarence) can be reassembled then. Old Boran needs to get rid of all of old Samburu before it is really safe to turn on themselves (with the possible exception of Clarence at some point).