Well since Foster's leaving anyway, getting him in a sign and trade while dumping Scal's contract would help both sides, although I'd miss Scal's towel waving. I say we just wait until he hits free agency - Foster's been close to a title a few times, and I'm sure he'd love to play for a contender.
I've liked Foster for a long time. I haven't seen him play all that much, but he is an excellent rebounder (especially offensive), shot blocker, and defender. Which is what a back-up center is supposed to provide. The biggest reason to get him in a trade is that it would allow us to use the MLE on Posey. If we don't get a center or backup PG in a trade, I think we will be stuck trying to get Posey to accept the bird exception, which would be 22.5 for 5yrs I think.
I think both teams would be happy with Scal, Pruitt, and the player picked at #30 for Foster. That deal would work if the salary for #30 is over $850k, which I believe it is. I would probably cave and do Powe in place of Pruitt if need be. He will most likely walk after next year because someone will pay him more than us, and he is redundent with BB. Another good reason to get Foster is that his salary is $5.5M, so you could package him with future picks, TA, etc at the trade deadline if you really wanted to. It would at least give us a few options.
After getting Foster, giving Posey most (or all) of the MLE, signing TA to the qualifying offer, and giving house a 2 yr 3.6M deal, we'd only need to get a backup PG. That could be pick #60 or a vet minimum guy (Cassell).
It really gets good if you find that Posey will take the bird exception. Then you've got what ever you want of the MLE to get a backup PG like Udrih, Pargo, Arroyo, or Duhon.