“… the controller has now put the decision into the hands of the pilot…” (#8)
This appears to be another of those situations where the crew’s responsibility for a safe landing is increased, but the crew may not have all of the relevant information.
Runway condition / braking action could be a significant factor, but the crews knowledge of these aspects is limited and in adverse conditions (wet, contam, etc) more likely to be incorrect. Even with a reasonable estimate of landing conditions the intent to land is based on the safety margins of the required landing distance (factored) and not on some indeterminate distance along the runway if the preceding aircraft is slow to clear. Accepting such a clearance implies a change to the briefed level of braking – who changes the auto brake setting, who remembers to brake harder immediately from touchdown?
Obviously if ‘the preceding traffic must be clear of the runway’ is a mandated prerequisite, then the runway conditions / braking action aspect does not apply, but as BigBoeing intimates, and from my experience, the US interpretation expects a landing with an aircraft still on the runway – peer pressure.
This is a dangerous precedent adding to the stress of operations and increasing opportunity for error or pushing the rules, detrimental to safety.