Currently, if the user wants to know the plan used for a certain statement, [s]he has to prepare the statement on a different attachment.
Depending on the number of statements, this may be an unacceptable overhead.
Plus, there is a change that some index changed after the original statement. The plan could then be different and the analysis compromised.
Please include the statement's PLAN in the monitoring tables. The most straight forward way I can think of is to include a mon$plan field in mon$statements.