I hope this post comes across as constructive and not a flame.
You are proposing a really bad idea.
First, how many of you got paid union rates or minimum wage for your first gig? How would you have learned enough to earn money from music if you weren't able to do freebies to get your skills up.
Second, I have a room where I play with two bands, a four piece and a twenty piece. By your rule the twenty piece would have to charge five times as much as the four piece. Not viable. That can only end in the twenty piece being put out of business, and I like playing in that band. Besides, that twenty piece plays music for a lot of oldies who want to relive the music of their youth (Miller, Dorsey, Ellington, etc). You are depriving them of that chance.
Third, it won't stop at a four piece taking work off a twenty piece. A three piece is cheaper again, then a two piece cheaper still. So all of a sudden, the pressure is on to come up with the smallest lineup that can do a band vibe, and along with drums, guess what instrument is going to be sequenced rather than played live in that circumstance. I'd be brushing up on keyboards REAL quick if the industry ever went the way you suggest.
So if you really want to put a majority of the bass players in this world out of work, and destroy the ability to play music with a large lineup, by all means find a lawyer who can make your dream - or nightmare - a reality. Just keep it in the good ol' USA, so that when it stifles your new talent and destroys your music industry we can export more product to you and have many more rich musicians here.
But I'd be interested how you defend the morality of this idea. Why should you destroy my fun and the fun of those who listen to my twenty piece just so you can get gas money? Ditto why should you destroy the opportunities for new musicians to start out? You are being at least as bad as those who you feel undercut you. Worse in my view...firstly because you are deliberately sabotaging the art of others so you can have gas money, and secondly if you EVER did a free gig you are proposing rules you were not prepared to live by, which is hypocrisy.
Strong words, and I don't want to upset anyone, but I have to admit your suggestion upsets me. (Could you tell?)