You can already do this with pistons. Just use a piston to move one block of the cannon to allow you to carry it. And you can just build a trailer unpilot move the block connecting it repilot and drive off. And if you build it right the trailer can be piloted it as a turret so you can control 3 guns at once and turn it. You can also make sure the trailer can be piloted as a truck on its own which lets you move it on its own.

If you want to see a design of this I have one in my plot