The only real argument for running a graduate only programme is to tackle the unique needs of this group. Operational, tactical and strategic modes - Identifying when to do a quick fix, when to plan, and when to challenge direction. Graduates require a particular set of skills to become effective fast. They have intelligence, confidence and 'attack' - the willingness to rise to a challenge. A prime focus of graduate training should be to practise skills in learning on the job.
Graduates are good at learning in classrooms.
They are not usually good at learning from colleagues, throwing themselves in at the deep end, or seeking feedback. All the learning they do on the programme should involve live experience, preferably on the job. For example, it would be better for them to learn simple presentation skills from observing presentations, talking to colleagues, or volunteering for presenting on topics to their team, and seeking feedback. Once they have mastered the basics and got over the fear, they will achieve much more from the standard Presentation Skills training. And they will also have practised skills in learning on the job which will be useful for their entire career.