I think he would be fine with Davis. They would complement each other:
Slow-footed big man with devastating midrange jump shot off pick-and-pop.
+ Solid rebounder, thanks to long arms and wide build. Decent handle for size.
+ Strong, smart team defender but overmatched against good post scorers.
Now that he can't run anymore, Brand has become Mr. Midrange, and did it effectively enough last season that he was still a very useful player. Last season he led the NBA in field goals from 10-to-15 feet with 159 and attempts with 325. To put this in context, he had about 25 percent more tries from that area than the next closest player, Dirk Nowitzki. He made them, too, making 48.6 percent, so nobody's complaining. However, one suspects he'll have trouble maintaining that lofty level, which is why he should expect his field-goal percentage and PER to regress about this coming season.
Meanwhile, Brand took fewer than three shots a game at the rim. He's no longer a dominating interior player, with middling rebound and free throw rates, and in particular he struggles to score against long defenders. However, the switch to jumpers reversed the plague of turnovers that descended upon Brand in his first campaign in Philly -- he had the eighth-best turnover rate among power forwards last season -- and as a result he had his best PER since injuring his Achilles. He's a smart player and these stats show it, as he made the necessary adjustments to compensate for his changing abilities.
Defensively, Brand still has long arms, a good base and his smarts, so the drop-off has been less noticeable. The Sixers don't let him anywhere near good post scorers, but as a helping big man he's effective and his physicality is beneficial.