Yoda??? What are you doing here?? Okay, comic-wise all of the Force ghosts have probably been following Luke around since Dagobah, but that wouldn't cover the movie at all. And we didn't hear from any of them until now anyway! I can't think of any reason for Yoda to suddenly show up again just to make a tree explode, that Luke appeared to be heading to destroy in the first place.

I'm actually a little doubtful that Yoda was the one to cause the lightning strike. Assuming he's closeish to his Episode V personality, I don't see him deciding to destroy a tree like that. Sally is more than happy to make things explode though. And of course, it's all a little too late there anyway. Rey most likely already took the records for whatever reason she's got, so the lightning won't do much good there. Which, come to think of it, is actually an excellent reason now for Luke to leave the planet now. Bit of a shame that Rey just left with the only functional and not-waterlogged ship on the island.

So! If we can get Yoda back on screen, maybe there's a chance that we'll get Force ghost Obi-Wan and/or Anakin as well. Obi-Wan would obviously be a mentor of some kind, possibly showing up for Rey. That could be good discussion, kinda like a grandparent discussing their kid with their kid's child. Anakin? Maaaaybe as someone with a warning about the Dark Side? That'd have to get twisted around for the comics though. Anakin never seemed to repent even after getting zapped in Luke's body by Palpatine.