I hope you would agree that it is important that fair criteria are used to select individuals for redundancy. If LIFO is one of the benchmarks used it should not be weighted more heavily than other criteria such as disciplinary records, attendance records (Absence for pregnancy should be ignored), work performance, qualifications, experience etc.
You appear to have more faith in unions than I do and few have faith in management. If the contract you sign does not meet with current legislation then it can be trampled all over. Legislation also changes and any changes must be reflected in an individual’s contract of employment.
At the end of the day this is going to be a fight about people keeping their job and those threatened with redundancy purely on the basis of LIFO should fight it tooth and nail.