I think Cleveland actually makes a lot of sense for Arenas.
Mo Williams and filler (boobie, sign and trade shaq, etc) for Arenas.
It would give the team a legit #2 guy and from what I've read Jamison and Arenas got along fairly well so there shouldn't be issues on that front.
Cavs next year with Arenas, West, Lebron, Jamison, and Varejao, with Big Z, Hickson, Parker, and Moon coming off the bench is a better team then they had this year. They could then use the MLE to get some solid veterans to fill in the gaps (Al Harrington, TMac, Rafer Alston, or guys of similar stature wouldn't be bad additions).