Papillon
It is an interesting debate. In my opinion, the current system does not work effectively. One of the unfortunate results of collective bargaining, is that those that do not pay, benefit from the generally improved conditions that unionised groups achieve.
It works well when you have a large workforce, but only a handful of roles. It does need both parties to talk though. Most people accept when they sign up to work for a unionised employee, that their T&C's will be union negotiated and that fact will appear in the contract of employment. If that arrangement is not acceptable, then they should not accept the employment offer. It is only one more step to make the requirement to pay for that contractually agreed position and therefore be able to vote on any variation.