Rangnick career can't be described without mentioning the acquisition, development and introduction of young, sometimes very young players to the first team. Keep in mind that he worked at a level where it's a necessity if you want to be sustainable, you need to produce young talents and eventually sell them at a profit. The difference for a club like United is that they don't have to sell players when they are developed and good enough for the first team.
On a side note, Rangnick approach or the approach used by Paul Mitchell and Ajax, which is to heavily rely on academy graduates and post-formation(players between 18-21 that need development and elite coaching) is something that was preconized by the ECA. It's considered as the most efficient way to manage a football club in the future because it reduces the amount of players that you purchase at high fee and homegrown/post-formation players tend to spend more time on inexpensive contracts which is good in terms of resource management. It's a model that Bayern try to follow.
So yes, the youth players should be at the heart of his concerns and if he stays these type of players should be the backbone of the club's logic.