The investigation of accident regulations provide for the removal of wreckage which could be blocking a runway in the circumstances described.
However since a licensed airfield is required for most training, should the fire services be depleted then it can take time to return to the minimum required.
While it is a legal requirement to have a map on board, if the flight will be wholely contained in the circuit then this can simply be a local map of the aerodrome vicinity. Thus the flight would be legal without any enroute map(s).
When considering the posibilities of when a diversion should be planned for think about the following;
Having decided to divert, there is the posibility that the runway at the diversion airfield could be blocked unless it is sterilised until the student has arrived.
Should the diversion runway become blocked or the fire service become depleted say due to a building fire, the student has used holding fuel getting to the diversion aerodrome and now is in the same situation as they have left but with less fuel to hold with.
The diversion flight needs to be properly planned in advance and thus plog, chart, PPR, fuel requirement, enroute weather etc all have to be prepared for every circuit detail.
My opinion is that the student should have enough fuel to hold overhead for 45 minutes and they should be briefed for the posibility of a runway blockage to fly the circuit at circuit height until it is safe to make an approach to land. (i.e. never send them first solo without at least 1 hour fuel in the tank)
Regards,
DFC