With my FS4 on the Mac, it does not work to set up a mouse as a control device
Yes, in Windows it is possible to fly with mouse and keyboard if no joystick is connected.
At the bottom right corner is a square icon you can grab with the mouse and use it like a joystick for pitch and roll.
Also there is a slider on the left side for throttle and an icon for flaps.
But ist is also possible to configure freely any keyboard-key for flaps, throttle and other stuff.
I can´t imagine why it should be different in Mac-OS, but ok, maybe it is?!
Grab anywhere else on the screen with the mouse is for look around.
Works very well.
Hope that helps.
Greetings!
Of course it works that way on a Mac too. 
I understood that the mouse should be integrated and configured as a control device, and that doesn't work, at least for me on the Mac. 
Now that you say it, you can understand the question even that way, probably right. 
I remember FSX had souch a funktion build in, but never felt good to me.
Greetings!
