The logic of IDP plan should be focused on areas of quick wins at first. The employee performance depends upon several different personal attributes: knowledge, skills, attitude and personal traits. As the knowledge is the easiest attribute to fix, probably it should be the primary goal of IDP. Still, other personal attributes should be considered for the IDP.  

The Knowledge seems easiest to fix. A simple knowledge may be sufficient. Classroom trainings can be a good solution for knowledge transfer. On-job-training is also a good way of knowledge acquirement.

The Skills takes time to build. They require training, practice, coaching and feedback. On-Job-Training is the best way for skills building. Classroom training can also help. Basically the knowledge applied through time become skill.

The Attitude of employee is more difficult to fix because it comes from culture and habits of employee. Those habits and culture were built probably even before the employee was assigned to current position. Intensive coaching and exposure to a new way of thinking can change attitudes gradually.

Personal Traits of employee are highly inflexible, since they are personal characteristics of an individual. The change of personal trait is not likely to be changed, especially on the short term. Although, the people can change over long period of time. For example person that was neurotic while it was young can became more emotionally stabile as it matures. The person that is introvert at the beginning of career can be more extrovert as it gains experience and knowledge during the career.