A non-aviation viewpoint, but with some experience in handling HR matters. How are the HR functions organised at your airline - is there a central function which applies policies or has it been delegated out to local management? If it's the latter, I'd definitely want union support - my experience is that this leads to inconsistency of approach and I've found TU reps have a better grasp of the companies policies than local management and - how shall I put it? - can help managers apply policies fairly....