Don't know about a mentoring program, but DE727 may have a clue. APC is a good mentoring program if you up and comers would listen to those of us that have been around the block.
There were a few in my class who had corporate only or mil only backgrounds, one flew freight in turboprops. I know of guys at FDX and SWA who were the same. By far, most fly at another airline first but it's not the only way to go.