Khorton,
You rather selectively quoted from my post - you will notice that I also suggested there should be improvements in training and crew rest requirements.
However, I stand by my suggestion. The information provided for pilots by the company for which I operated the Q400 indicated that with an increase of Vref of 20kts the landing field length had to be increased by 25% - this may seem a lot until it is remembered that for a Q400 a flap 15 landing on one engine at max landing weight only requires 1360 metres on a dry runway, or 1700 metres with the "increase ref speeds" switch on.
This has to be taken into account whenever the switch is on, be the re-bugging of speeds be done manually or automatically.
Obviously if the runway is contaminated or the braking action not good that must be taken into account, but I would suggest that most (not all) destinations being served by Q400s would not produce any problems.
I see from your profile that you are an engineering test pilot. If you work for Bombardier, could you guess at how difficult the software changes I suggested would actually be?