Whirly, I don't have a straight answer to your question. It still comes down to risk management. Take your scenario - the answer depends upon:
How many runways are available
The need/desire for fire cover
The number of other aircraft in the sky
The diversion options
etc etc
My point is that we can be overly protective as a result of not making a sensible risk assessment. There are obvious things that must be taught and demonstrated to a satisfactory standard. There are others that seem to have been developed as folklore (I've seen instructors insist on short/soft field techniques prior to first solo). Alternatively, we can adopt the Health and Safety, "No" culture.
As I previously said, we shouldn't create false milestones based around time to solo; the markers should be a set of clearly defined and reasonable criteria.