“Taxiways are all capable of taking a landing in such an unlikely emergency that you cannot hold while the clearing the RW.”
Try telling that to ATC in many Asian countries. Good luck.
“2. You having absolute min fuel, ie you have used your contingency”
This will always be the case. If a large aircraft in front of you has a nose gear collapse for example, then no airline will have enough fuel to hold 24 hours while they move it. 30 minutes gas up your sleeve in this situation will do very little for your outcome. Much easier to have a plan B in your pocket I reckon.