1. we'd have to hope beyond hope that whoever's available with the Lakers pick would be anywhere near as good as Rondo.
I think this statement would be true if it weren't for Rondo's impending free agency. A year from now, Rondo will enter free agency. First of all, he'll want a max contract. Second, he'll want to sign with a team that is ready to be highly competitive over the length of his contract, since his contract will encompass what remains of his prime.
Even assuming that Rondo is worth a max contract (debatable in my opinion), the Celtics may or may not be in a position to offer Rondo that kind of situation.
With that in mind, getting a really significant return value for Rondo this summer (a top 10 pick in this draft certainly counts) might be preferable to taking the risk that Rondo bolts in the summer of 2015 with the Celtics still looking to be a couple of years at least away from being ready to truly challenge the best teams in the league.
From that perspective, it's not a deal-breaker that the player you're getting back in the deal isn't necessarily going to be better than Rondo is at his best.