We're arguing 2009 Shawn Marion vs Iggy right now, so it's not really anything more than me implying you need a real scorer. Iggy is an upgrade over the current Shawn Marion, no doubt about it.
As far as 2009 Marion taking anyone off the dribble, it happened when he would spend time at PF. Marion was also good at getting to the rim by spotting up for three and then driving the lane after the ball rotated to him.
Either way, it would be an upgrade to get Iggy, I just don't see him being e type of scorer Dallas needs to pair with Dirk. Teams don't want the ball in Dirk's hands at all...with Iguodala, they'll gladly let him have the ball and give him the 15 foot J.
There's a reason Philly wants to move on.