All TUs are dependant on their members.
There is no "wand" to be waved.
So if members want something to be different, they need to take action.
A TUs only power is the threat of IA. If a TU wants to get an employer to do something, it needs a realistic threat of IA. Very few TUs have that nowadays.
I was intrigued by a dispute outside Aviation - in Pharms. Astra Zeneca closed their pension scheme to existing members. No more pension accruals, although old accruals would be honoured.
Astra Zeneca ER folk and their bosses were clumsy in the extreme. (Take it from me, AZ bosses are a thousand times better than Aviation bosses. But in this case, they were not very good.).
They forced the TUs to hold strike ballots. The TUs won the strike ballots - and held some of these modern day-long strikes. AZ ignored them.
AZ "won" the dispute. The employees lost.
Moral of the story - even if you do go on strike, it doesn't mean that you will win.