I was thinking about this earlier today. I would love to see Luke and Rey discover a "light side cave" and inside is a giant Force crystal that majorly amplifies the Force - powerful enough to manifest the spirits of the dead within itself. Leia touches it and Han appears, and they are visiting as if between glass, he tells her he loves her, she smirks, and with a tear rolling down her face, replies "I know." He steps back into the nethercloud inside the crystal. Then Luke touches it, and Padme appears, the mother he never knew, him now an old man, her still young and beautiful. She is visibly overwhelmed, "Luke.." He knows who she is instantly. "Mother.." They have a tender moment, he has so many questions..

Later in the film, Kylo Ren, who has been tracking them, comes upon the crystal.. He is met by the ghost of Anakin Skywalker inside the crystal, his grandfather who he looks up to so much. However, what Anakin has to say is not what he wants to hear. Anakin tells Kylo that becoming Vader was a mistake, that he lost everything. Kylo becomes enraged at being abandoned by the spirit of even his greatest idol, ignites his lightsaber and destroys the crystal, shattering the hope of Luke or Leia ever visiting their loved ones again and causing a massive blow to the living force.

Just a daydream.. But I would love to see something like this, that allows for a bit of crossover between prequel and OT characters through the Force, I really like the idea of seeing Luke interact with Padme or at least find out who she is, he was asking about her at the end of Jedi and I hope he gets his answer.