RasputinLives Mercedes signed Ocon on their young driver programme around the time Wehrlein had testing with Mercedes at 19 I think as development driver and testing experiences with Williams and Force Inda as well. Wehrlein was probably thinking he was the future golden boy and Ocon was a threat to his position
F1Brits_90 RasputinLives Mercedes young drivers programme had always been based on fielding teams or pairings with one experienced driver and one junior driver outside F1.
M Schumacher felt his experience with Mercedes was great for his development because not only did he experience how a big team functions, he had experience to lend from his senior teammates but he also learnt how to deal with the press and the pressures
Like you said in many ways the young driver programme helps young drivers to fit and model themselves to act as a corporate representative for Mercedes in future longer term
When it comes to getting drivers into F1 apart I can only think of Heidfeld and Zonta who were doing F3000 and then progressed into F1 with testing experience from Mclaren but the others are coming through DTM - Di Resta and Wehrlein.
However it also seems like doing DTM for some young drivers is a good way to make a career if they can;t get into F1
i think drivers like Jamie Green and Gary Paffett - the latter certainly had the talent to be in F1 but doing DTM did not help increase his chances of getting into F1 other than testing with Mclaren when maybe doing F3000 might have helped
T