I would love to see the Angels replenish their farm system with prospects from other organizations, but this cannot be done unless you are prepared to miss the playoffs for the next five years.
You are only going to get top 10 prospects from other organizations if you trade the players we do not want traded. This means you would need to give up any near future playoff hopes.
You can get great prospects for Weaver, Trout, or Trumbo, and maybe Freiri, but if you take these four guys off the roster, the Angels would be 10-15 games under .500 and already out of the hunt this year. You would gut your short term future as well. Trading these guys would be absurd.
The Angels would not get much for any other players on the their ML roster because they are not good enough to command top prospects and/or they have long or overpaid contracts that no one else will take on.
I guess what I am trying to say is the Angels are stuck with what they have, unless they want to further gut their future by trading for more "proven" veterans in exchange for Bourjos, Cron, Calhoun, etc.
I hope Dipoto will resist this temptation and rebuild the farm slowly through the draft and hold onto the young promising guys they have.