One big concern is you will have to leave the helm to use the outboard. If you really want "extreme control", install a bow thruster
SS340 Bow Thruster
The price of the bow thruster is about 25% more than an outboard but will give you much better control while increasing the value of your boat rather than decreasing as an outboard would. I personally would not buy a Catalina 320 with an outboard mounted to the back.
One reason I am being so persistent about this is an experience I had a few years ago. I was sitting on a friend's boat, a few down the dock from mine. A fellow in a 22ish foot sailboat with an outboard was coming down the main harbour, making the turn into the inner harbour which is right where my friend's boat is. Another boat was coming out of the inner harbour at that time and the fellow on the 22ish footer didn't see this outgoing boat right away. At the last minute he jammed the outboard into reverse and tried to steer away using the outboard, but didn't coordinate his movement with the main rudder, and ended up drifting down on us on my friend's boat. We fended him off, no damage, but I muttered under my breath "oh no, he is heading towards my boat now". I think the fellow might have heard me so he jammed the motor into forward and spun it to maneuver away at which point the outboard flipped off it's bracket, did a pirouette and disappeared under the water into the depths of the harbour.
The entire thing was rather comical, and there was no damage other than the loss of the outboard. I went aboard my boat, helped him along side until he gathered himself up and he pulled out a paddle and went on his way. He thought he could maneuver the boat using the direction of the outboard without consideration to the direction of the main rudder. That clearly did not work. He was better off with the paddle than the outboard.