Controller handling different input types

I have a use case where I want to have a four wheel steering controller. I was planning to write a new one and adapt it off of the tricycle steering controller. My problem is that my use case has an autonomous mode which uses nav2 to output a Twist command, and a manual mode which outputs a linear velocity and turning radius. The problem is that I can't think of a clean way for my controller to handle both of these modes (only one mode will be activated at a time) because they each have different topic types.

I've tried thinking about whether I could use a ros service to listen to autonomous mode and switch to listening to a Twist command, or dynamic parameter change. But honestly not too sure.

I've also considered chaining an Ackerman four wheel steering base controller with an Autonomous mode controller and manual mode controller to each handle their different topics.

I contemplated propagating the turning radius from manual mode through a Twist message (but this is ugly), and vice versa for autonomous mode with an Ackerman drive message.

The use case is a four wheel Rover with four drive motors and four pivot motors.

Review the issue discussion and linked pull request #1563 first; no source file, test, or entry point is named in the issue. The work is not ready for a newcomer until the controller interface and expected handling of autonomous and manual inputs are agreed, with completion criteria documented.