If this were Votto + Cahill for Bruce + Zimmermann, I might be on board.
As it stands, you're getting similar production from a position easier to produce at. 1B has some of the best players in the game producing like mad. OF has several too, but it's easier to find an elite 1B than an elite OF. (In my opinion anyway....)
Cahill for Zimmermann would offset that perceived loss in my mind, as Cahill should be an upgrade over Zim.
Wanting Hanson too is ridiculous. He's trying to fleece you hard. Even if this was Votto/Cahill for Bruce/Hanson, I'd say that's too much. If I remember right, you did say bruce can only be kept until 2012 whereas Votto could be until 2013. If he will only trade if he can fleece you, that extra keeper year is NOT worth it.
Don't do the trade. And frankly, I would just tell him I'm not interested with trying to work out a trade with him. He'll only trade you if he can get the drop on you, so just don't trade with him. I have people in my league like that too. (Someone just got Adrian Beltre off the 10th place team for Kyle Lohse... I don't see how that's even possible without some serious pushing....) I just don't try with them.
Anyway, hope you find a trade that works, but I don't think it's for Votto.
if you want to take a stab.