If the Raiders lift the tag, there is no need to offer any trade compensation. They lose the right to trade him if he becomes a free agent, unless he would have been restricted before recieving the tag.
I do agree with you, but the Raiders have proven themselves to make a life a living hell for any player that tries to cross them. Also, I highly doubt the Raiders want to give any of their division rivals the slightest chance of having to go up against Asomugha twice a year. I look for them to try and work some sort of deal. Remember, there is no RULE saying that a team has to give up two #1's....it's just a rule of thumb. It's whatever the two teams in question agree upon, since he is "franchised."
Again, I can't see the Raiders just lifting the tag and letting him walk. They have too much ego and have always been the team to make their players pay the price for not toting the Raiderr Company Line. Al Davis would ship him off to Japan for an 8th rounder if he thought if would make his ex-player's life hell. He always wants to set an example to others of being someone not to mess with.