Just some additional feedback as I've played some more...
I saw some people want to have the school-wheel loop, but I think the main solution is to have a clearer difference in the design of each weapon on the tank (different colours/tone or something).
And possibly having a weapon icon as a UI element just below the tank as you're switching so you can see what you are changing to - it could fade in and out so it's not always there potentially. It's hard to look in the bottom left of screen while you're fighting.
And lastly, it'd be great to have keyboard numbers 1,2,3 bound to weapons so you can go straight to the one you want to use.