Obviously, the first and foremost question would be, "For how much?"
I think for something like the Lesser MLE or less, it's a no-brainer. Two-three years for a sunset contract. Easy. For more money, it gets a little grey-area.
Rebuilding doesn't mean you don't need veterans. Especially experienced veterans like Pierce who have a lot to offer when it comes to mentoring. He'd be basically like having a "player-assistant-coach".
Pierce has pretty obviously grown way past the I-have-to-take-all-the-shots ego from years ago so I don't believe it would create any problem with disrupting the usage and development of the younger players.
If we don't pick up a young SF out of this draft, having PP to now be the backup _behind_ Green would be solid. If, however, we pickup, say, Parker - then maybe there is a log-jam.
And of course, it would definitely not hurt ticket sales.
On the other hand, Pierce may still feel he has something to offer a more obvious contender still. And given the way he has been playing in this half of the season, I would not be surprised if a few teams still want him.