My main concern with Okafor is that he was injured for most of last season, and the Cs have had way too many injury issues the last four seasons, and even being young hasn't seemed to hold the injury bug at bay (see: Bradley, Avery, and Green, Jeff).
Still, Okafor is a solid center—a good rebounder and defender who's also decent on offense, and picking at No. 10 would greatly increase the chances of the Cs getting an impact youngster. If it's Rivers, that's cool—he knows how to score, and we all know Boston is in desperate need of a scorer. Boston also needs rebounding help, which Okafor would provide. Plus, his contract is up in two seasons, so he, Pierce and a re-signed KG could all go off the books at the same time. This year's free-agent class is a dud, and next year's could end up being the same. Start Okafor and KG, have Bass, a re-signed Wilcox and a re-signed Stiemsma on the bench, and suddenly you have a pretty good, and pretty deep, frontcourt. Have Green backing up Pierce, and a backcourt rotation of Rondo, Bradley and Rivers, and you've got a good mix of youth and experience, and plenty of guys who can run with Rondo in his prime, and still an overall good defensive team.
Of course, I don't know if my scenario fits financially, and I'm not saying Boston SHOULD do this ... just an idea.
PG: Rondo/Moore
SG: Bradley/Rivers
SF: Pierce/Green
PF: KG/Bass/JJJ
C: Okafor/Wilcox/Stiemsma