What exactly are you looking for?
Before you start a mentoring programme, I think you should decide what sort of pilot/employee you are looking for. Once you have decided that, then the programme can be written.
I'm presuming all of your pilot's can fly (That's not the case with every airline!). That they know various bits of aviation law. But I bet they are not natural managers nor do they know what do to when things go wrong from a people side of things. I'll also guarantee they don't know how their company works nor what their company wants of them. They might also be lacking knowledge regarding civil law as it relates to aviation and the niceties of how to minimise exposure to (social media?) criticism when the inevitable happens. If they fly internationally, a good grounding in what happens overseas (legally, culturally, etc.) might also be useful. I'll also suggest they don't know what help is available to them when they need it nor where they should go when it is required.
So when you know what sort of pilot you want, a programme can be written to move your guys from where they are now to where you want them to be.
PM