Why do you guys have more than one union? It's simply not allowed in the USA. You have one bargaining agent who is certified by the government to act on your behalf. That prevents the workgroup from being whipsawed by management.
I don't say that our system is better but I can see the pitfalls in yours. And I say this from the perspective of being under a union that was very detrimental to myself and the other 1400 pilots in my base.