We know that Luke Skywalker vanished after
Kylo Ren killed his students.
But, for some reason, there’s a map to his location. That seems odd for someone who doesn’t want to be found, at least not by the wrong people.
Throughout the movie people kept calling it a "map to Luke Skywalker" but I think they were being a bit sloppy with their phrasing.
At one point, Han mentions that everyone believes Luke left to find
the first Jedi temple.
The map everyone is looking for, then, isn't a map to Luke. It's a map to the thing Luke was looking for. This is significant, because two different characters have most of the map already:
Kylo Ren tells Rey this, and R2-D2 displays it at the end.
Both characters got this map information from the Empire's records, so clearly the map predates Luke's journey by a long time. In fact, in the novelization, one of the Resistance members makes this same connection, after being told that the Imperial Records had the rest of the map:
'Admiral Statura nodded in agreement. “It makes sense. The Empire would have been looking for the first Jedi temples.'
What's missing from this map -- likely, missing from the Empire records -- is the last piece. However the Empire got this map, one section of it was lost/damaged/never scouted/etc. That is the thing that was found at the start of the movie and that everyone else needs to find Luke.
I assume the overarching plot is going to be that Luke is a Chessmaster implementing a Xanatos Gambit against the Dark Side.
Consequences: If my cached Force user arrives at my location shortly after the major Force ripple, it will be time to set out to shut down the Dark. Otherwise, continue hiding.
This answer may be colored by the pre-Disney writings about Palpatine's Xanatos Gambit regarding defending the Galaxy against the Yuuzhan Vong.
This was the most unsatisfactorily handwaved part of TFA for me
I actually didn't feel that it was handwaved at all. When I watched the film, I perceived R2's activation as a complete, and totally unexplained, surprise.
Commented
Jan 5, 2016 at 13:22
I took it as, "I don't want to be found, but if you really, really need me, here's where I'll be."
Sort of like giving co-workers your private phone number when you're going on vacation.
I think you answered your own question. He doesn’t want to be found by the wrong people, so he created a two-level authentication challenge that presumably, only the right person/people/Wookiee can complete. Finding the fragment is the first part, but anyone can do that. The second part is to get R2-D2’s approval. Those requirements are never made clear, but the implication is that R2-D2 must validate that the right person and/or Wookiee found the fragment. You can infer that Rey is the right person, as R2-D2 failed to activate until she presented herself.
distance / hyperdriveRating
thing - some routes are inherently faster, while others are inherently slower (I assume major trading hubs exist on places that have plenty of fast routes). The former EU goes even further, and explains that hyperspace routes are discovered, rather than "calculated" - and discovering new routes is shown as extremely dangerous business. Most likely, plotting a course in hyperspace is actually finding the fastest path in a graph of known nodes and edges.