Let's not forget in all of this, that even the BA NAPS scheme is still about 80% funded, and it is the deficit we are talking about, which is a notional long term issue.
The valuation process is designed to identify a way forward.
The pension deficit does not impact directly on the ability of BA to trade, but the size if the funding required to satisfy the regulator and the ability of BA to pay will determine the split between the money BA pay to service accrued benefits and future benefits. This will drive the changes necessary to future benefits. It is not necessarily cheaper to discontinue the scheme.
That's as I understand it, anyway ....