Okay, it's been...a while...since I played ZT2, but I've been thinking about it quite a bit lately (still have the Complete Collection installed) & was actually just thinking about this very thing.
While I personally feel that The Sims 3 sucked big time (just my opinion as a hardcore TS2 fan!) I think that a properly done Zoo Tycoon 3 would be pretty dang cool, especially if they managed to combine the best features from both into one game. (The thing I missed the most from ZT1 was - of all things - the ability to name the exhibits. I really, really enjoyed that!)
So yes, I would likely sign any ZT3 petition I found, if only to let game designers know that some of us folks really do enjoy games that aren't all about stealing cars, killing cops or beating the tar out of things!
(Still thinking about booting up ZT2 again...if I can remember what I used to know about modding it!)