Maybe one answer is to use a bigger safety factor when landing on contaminated runways in this type? It seems strange that there is no mention of an override: at least with most implementations of thrust levers, if you push them as far forward as they go, you get the most the engine can produce, even if you’re using reduced thrust at the time. If you yanked the reversers back all the way, you’d hope the system would recognise that was what you wanted, irrespective of everything else. Like “ground contact imminent” when airborne.
I too have had a pucker-factor 50 moment landing on a slushy runway and having to rely on full reverse to bring us to a halt ~50m short of the end, due to the braking action being very different from that reported. We might have made it going to idle but it wasn’t research I wished to conduct at the time...