Ehh, the original three being back together on screen wouldn't have really worked for anything more than fan service.
Fan service? Did it make any sense in respect to how ROTJ ended that Solo would end up going back to being a two bit smuggler or that Leia would stop be a diplomat and leader of the republic and go back to leading a small rebel force or Luke would just up and go off by himself?
None of that really fit with their characters and where they ended up by the end of ROTJ, these were people that would have naturally stayed in touch throughout the life, so no having them on screen at one point in time in the new trilogy would have in no way felt like simply "fan service" to me, it would have felt logical and like something those characters would naturally do. Have Solo still be by Leia's side and have Luke come visit from time to time while he's out training or an an adventure.