If he wants to be a Celtic so bad, offer him last year's salary + 20% (that's the most we can offer, I think) and see if he'll accept it. I might be wrong, but I think that would just about be the same as the BAE, anyway, and the C's need to reserve that to use on a big. It won't get a very good big, but with the MLE already committed it's all the C's have left.
If Pietrus wants more, he's going to have to wait and see if the C's can bring in a big without using the BAE. If so he can have that, if Danny offers it, of course. If *that* isn't enough, then he won't be a Celtic this year. That's just the way the money works out.
Personally, I'd like to get both Lee and bring Mike back. I liked what Pietrus was giving the team between his knee getting a bit better and his head being bounced off the court. Before and after, not so much, but that's understandable. As for Lee, at 26, he could be both a long term piece and a short term piece.
A Rondo/Bradley/Terry/Lee back court quartet to go with a Pierce/Green/Bass/Sullinger/KG front court quintet would be a very strong rotation over the next 2 or 3 years. Having youth and experience in the rotation and on the bench (Pietrus, Joseph, Melo, ?Wilcox?, ?JJJ?) would form a bridge into the post KG/Pierce years. The C's would have good assets to use in trades for the next superstars and experience complementary pieces to put around them.
Probably, a pipe dream, though. I doubt the C's can snag Lee and I doubt Pietrus wants to be a Celtic more than he wants a bigger payday.