I started on such a master selector, but decided against it. The better solution is as I mentioned above, is to have a tool like the master selector able to reconfigure your ROS shell environment for you (we did by configuring a ~/.bashrc.ros and pointed our ROS setup.bash scripts to post-load that. That way every program, launcher and ROS shell utility will work out of the box. It is very rare that you’ll be interacting with just one rqt program, so embedding the master selector in the rqt wrapper means repetitive selection for each and every rqt wrapped program and then you will probably want to reconfigure a ROS shell for command line tools anyway.
A master selector is good for a program that doesn’t require a ROS shell, e.g. vanilla qt ROS program or android app.
Note: RQT programs are typically ROS shell dependent since you need the PYTHONPATH and rospack discovery to find most of them.