But, if the class is defined in the catalogue as 'Planned' then managers can 'enrol' someone in the class but it isn't a real enrollment, it just identifies a need or it guages the interest in the class. If there is enough interest, the administrators can change the class status to 'Normal' and then people can enrol and be placed on the real class.
Hopt this helps.
OLM doesn't really have the functionality for 'requesting' a training course which is not in the catalogue.
The method you could use within the standard functionality is:
Administrator creates a course which is 'Planned'. People can then express an interest in the course by making a 'reservation' enrolment request. If enough demand is there for the course, then the catalogue administrators can create a 'normal' course and enroll the people who expressed an interest.
As an alternative, do the planning outside OLM and when a course is scheduled, enrol learners on to it.
Other than that, you're really looking at an extension or customisation.
You could also create a "request training here" survey in OLM that users could enroll into and launch that would have questions in it for managers etc to enter their training requests that could then be reported on for planning purposes.