Hi CENTO
All things are possible. You will find almost ALL RC systems handbooks are written with aircraft in mind. On my tug, I use left side vertical stick on transmitter (with no spring return to center) as throttle (main drive on my single screw) the right side horizontal stick (i think normally ailerons for aircraft) i use as the rudder (with self center). From there on different people have different needs :-
Right side vertical up(self center) I use for horn, horn sounds when I hold the stick up.
SWitched channel (aircraft undercarrage) I use to switch navigation lights.
I don’t have mixers etc set up but I’m an old modeller and don’t appreciate all these electronic gizmos. Most of the guy’s in the model club I’m in seem to use left hand for throttle/sail controle and right hand for steering as above, but for other functions its what you are comfortable with. Twin and multiply props vary from modifying Tx layout (not for the faint hearted) to fully intergrated rudder/throttle mixersthat modify the inside and outside prop speed when turning.
If you are a member of a model boat club I’m sure there are members who will help and advise. If you are not in a model boat club I would suggest you try to locate one in your area. There are usually some very knowlegable people there
Best of luck with your tug (I have photos of mine on the gallery)
Cheers Telstar