I like Harkless a lot, and even have a signed jersey. But, some realities:
1) It would be better for the team to trade Harkless and get value back (a pick?) than it would be to give away a pick to get rid of Crabbe. The team is better with the Harkless trade. Crabbe + draft pick > Harkless - draft pick.
2) Harkless is a great athlete, but he is entering Meyers territory in terms of having all the opportunity anyone could want, and not breaking out the way we would hope. He is still young, and if we keep him I hope he does because I really like his game. But, so far that hasn't happened consistently. He may never get there, and if he doesn't, then trading him now would be a good move.