Dynamic Controller Creation in Rails
Disclaimer: this should be a comment, my reputation at the moment does not allow me to comment your question

What about exploiting const_missing? 
https://apidock.com/ruby/Module/const_missing

I used it in an app to declare ActiveRecord models at runtime. If you are interested in this approach I suggest you to namespace all Dynamic controllers i.e.

module Dyn
  def self.const_missing(sym)
    # Declare class Dyn::MyDynamicController
    # without overriding or patching Rails classes
  end
end