Your solution is fairly straightforward. The question is whether or not you are willing to take the step. You really answered the question yourself, and if you reread your post you will see the answer.
This isn't about friendship, it is about the music, and it is about what your goals are. Those are three separate issues. If you want to go pro, and they aren't willing to make the necessary steps, then someone has to leave. If you are willing to settle for it as it is, then prepare for the old pro bass player to leave and you will be doing what you have been doing.
It appears to me that you know you need to go and reconfigure your band, and you want us to talk you into it. I would encourage you to sit quietly, listen to your inner voice, and then make a decision based on your aims, and love for the music.