The MLE (if there's one) should be used to solve the biggest hole, that is having a backup for JO who can play 30 plus minutes if/when JO is injured again (hopefully never but...).
If they can get a quality defensive center like Samuel D'Alembert for the full MLE, they should spend it. If not, they might get Kwame Brown for 2-3 mil a year. Keep the rest of the MLE for the trade deadline and released free agents signing chances.
IMO, Baby doesn't deserve more than 2-3 mil a year. Maybe some team will overpay him, more power to them, but the Celtics won't offer more than that. He wants more money and the spotlight, so he probably won't resign with the Celtics.
He played great against Orlando in the 2009 playoffs. He hasn't played that good except for game 4 of the 2010 Finals. He is not a starter, but he's very talented, inconsistent but sometimes brilliant. But last year he played terrible ball, maybe he was injured, maybe it's just he's not as good as he thinks he is. Danny and Doc sure know better than us, and they will offer the right money.
If Baby goes away without a S&T, they shouldn't use the MLE to replace him. Give JaJuan a chance, use Jeff Green in smallball mode, and maybe Troy Murphy or some veteran for the min. They need the MLE to get a Center.
If Rondo is healthy and finally has got over the Perk trade, that's the most important piece for the Celtics. Baby is a very good role player, but he's not the key for our team.