Playing on a regular basis is also really important for his development. I agree sitting on the bench is not going to do him any good. He's still probably unlikely to get regular first team game time, So playing for the second team for periods is still a really good option at Bayern, especially in his first season there. They know what there doing there at Bayern. I'm sure they want to develop him properly and then sell him on for a killing in a few years time.
Bayern aren't a selling club, they don't think like that. They want trophies, and if they think you can help get them, they'll keep you. If they don't, you're gone by lunchtime. Just ask the Korean dude they brought over as an 18-year old whom they've now offloaded to Freiburg.