While I do do not think that NATS management has ever had the b$%$s to admit they were wrong, and that not a single one of them would ever stick their head up above the parapet and say, "Hold on a minute, this is crap". I will enter into the spirit of your topic, as it is admirable.
1/ Delay the O date. The training of staff for one is dangerously flawed. Apart from the high workload now put on ATCOs which is both operationally questionable, and a health issue. To ask ATCOs to sign off as competent on a new system with so little training, is dangerous. Personal pride makes most resist the temptation to refuse to sign on the dotted line.
2/ Re-work the concept of operation. For one I feel that the Local Area Supervisor Position, is nothing more than a get out for employing LATCC Chiefs who would be unable to validate on the new, or any system. No other unit in the country works like this. It is not revolutionary, but a step back to LATCC. What can the reasoning possibly be, apart from jobs for the boys.
3/ Ditch completely the NERC Software. It is cumbersome, time consuming, and an excellent examle of the system dictating the operation. IT SHOULD BE THE OTHER WAY ROUND. I am discusted by it frankly.
My solution then is:
Admit that NATS got it badly wrong and buy off the shelf. Forget the British Bulldog approach of continuing on in the face of adversity. Look where it has got us already.