I don't think the first action would or should be a walk out.
We already have a strong vote of favour of some sort of action over the OJTI issue and that is part of the pay deal on offer. Training ban? Disruption of unpaid duties? And I don't really think that management using this as an issue to blame us over NERCs delay is an issue. Management blame us and what? They still have a centre that doesn't work, an outstanding pay deal and an even more hostile staff.
Nor do I really think public support is important - the issues are complex and I doubt The Sun or The Mail will cover the situation in depth, so lack of public support is probably inevitable. But since any major disruption, if it got that far, would undoubtably be short lived as heads will be knocked together rather than the airlines lose millions in lost revenue. I agree, if the union recommends (or not) agreement and members vote against, then they should be prepared to do 'something' rather than 'nothing' to support the union.