IMO If you are trying to run a cover band playing in bars like a democracy you are not approaching it in a professional manner. Doesn't mean each band member can't have a professional attitude, but IME a professionally run cover band is a BL leading a group and group members doing what the BL wants them to do. If that includes bringing up guest singers and players, pros roll with the punches and do their best to make every performance a winner. If the conditions laid out by the BL are unacceptable, a pro will tender their resignation and (within reason) will continue to hold down their spot until a replacement is hired.
If it is an original music project and every member is involved in the creative process, then you should all have input and direction/vision/performance expectations should be a consensus among members, but playing covers in a bar, a pro bar band needs a boss to make the decisions and a group of players willing to work under those conditions. Does not mean individuals are not allowed an opinion, but it does mean accepting the decision(s) of the BL or giving notice they need to be looking for your replacement.
Nothing wrong with a cover band toiling under the "one member one vote" method, but again IME part time players in a cover band run like an originals project is begging for trouble and drama unrelated to the actual goal of making a little pocket money with minimal hassle, and if the goal of a cover band is anything other than making money, it should be approached as a fun thing that just happens to generate a few bucks while we all have fun and enjoy the hang.
Please understand, i am nowhere near a professional musician, i'm just a retired machinist who enjoys playing bass, but i am also a mature adult who understands there is little creative process required to parrot a familiar song for people to enjoy while they use your musical backdrop as an excuse to ask potential temporary sex partner(s) to dance while attempting to increase the odds of success by plying those prospects with strong drink. Don't get me wrong, there are plenty of professional cover bands out there, but they operate more like a business. The creative aspect is generally focused on marketing the brand rather than making a unique mark on the music world.
There is no bright line dividing pro cover bands from ham and eggers, it's really more a matter of how the thing is managed than how things play out in performance. A good BL insures the entire package puts it's best collective foot forward, everyone else is there to support that effort.