Hi,
yeah, that one is going to be tricky unless you create your own fps controller where you can override the values to make it turn programmatically...
try this:
Make another dummy level between your fps controller and your character visuals, you can then have the intermediate dummy to have your visuals to smooth look at a target without touching the fps controller itself, which anyway turns relative to itself, so you should be able to achieve this.
Bye,
Jean