My best guess is that his ending is necessary for tying together all of the routes. If it ended any differently, people who got a different ending wouldn't have any sort of closure for certain events on Leo or Jenna's routes. That being said, of course I wish there were an alternate ending for him (and TJ for that matter).
As for the five years later thing, those college kids are in every ending so far with the exception of Carl's I believe. They'll be part of a sequel that the team is working on!