Andre Miller won't require in excess of $12 million per year. At his age, he's not worth it if that were his demand. Letting Frye, LaFrentz, Ruffin and Blake go would be sufficient to free up the room for Miller, assuming he wants to play for Portland. Sessions can't be offered more than the MLE by anyone (including Milwaukee), so there's no need to cut Outlaw loose for him. I suppose if you wanted to try to sign both Miller and Varejao, you'd need to cut Blake and Outlaw loose, but you have to renounce them before the free agent signing period...which means you're gambling that you can get them both. I wouldn't take that gamble. Teams rarely sign every free agent they want, even if they have the cash, plus I doubt Varejao would want to leave Cleveland.
Ultimately, I don't see a big benefit to letting Outlaw go. If you think you can get Miller, letting Blake go makes sense, because Miller takes his place as the veteran point guard. But I don't see that there's value beyond the money freed up by LaFrentz/Frye/Ruffin/Blake.