As far as the Derozan trade, I don't mind the idea of getting Derozen, but I don't want to take Bargniani back. I've been mixed on Demar for a while. I really wanted him coming out, then he struggled a bit, then it looked like he was going to break out, then he regressed some again last year. I think he's an alright player, I don't know that he really makes this team any better than it is right now. I just don't want to do that trade if if means we end up with Bargs. He's not that great, and he's overpaid. He's basically Ersan minus the hustle on the offense glass and the willingness to take charges, but he's owed a whole bunch of money.
Interesting note if you're a fan of advanced stats though. Derozan has been better than Monta as far as offensive win shares go this season by a decent amount, but Ellis has actually been fair amount better defensively. So one could argue you're actually incorrect in saying the offense stays the same and the defense improves. If anything, this says the offense gets better but the defense gets worse (however I understand basketball advanced stats aren't perfect yet either.)
Edit: So I guess in theory here is a trade I would rather attempt. I hate pretending to be an unbiased trade person because I usaually rip one team off hard, but a deal of Ellis for Derozan and Linas Klieza works financially. I'm not sure how Toronto would feel about it, but I would be a fan of that deal.