This is the most even trade I could come up with. Danny (if healthy) is much better than Hedo (if healthy) but Big Baby is much better than Ian even at less than 100%. The Pacers would basically do this deal to get an upgrade at backup Center which is a bigger need than what Danny provides at SF.
Danny and Hedo are both on the last year of their deals so the salary is pretty much a wash. The Pacers only take on an additional $378k in salary for this season and will still be a couple of million dollars under the luxury threshold.
I'm not advocating trading Danny but in some ways I think the Pacers need to address the back up Center position because Ian just isn't very good.