I believe City's plan for these 'City Football Group clubs' is very different compared to what the Chelsea owners are trying to do.
For City the satellite clubs are more or less just about raising their global brand but with Chelsea the vision for Strasbourg, and potentially other clubs later on, is much more closely linked to player development and talent scouting. Rather than the example of City the idea seems to be more in line with the Red Bull organization who regularly have players make the step up from Salzburg to Leipzig.
Notable players who have moved between the two RB clubs in recent years include the likes of Peter Gulacsi, Konrad Laimer, Dayot Upamecano, Amadou Haidara, Naby Keita and Benjamin Sesko. That's not a bad record at all.
Some players will be bought by Chelsea and put on the loan route with a few spells at Strasbourg to either develop them into being good enough to make the step up or be sold for profit later on to help with FFP. Others will be bought by Strasbourg directly and if they prove themselves there they can then be transferred to Chelsea at a price tag that will be less than the same player would command on the open market, due to the clubs being owned by the same party (this is what the RB clubs do all the time). It's dodgy as feck but as long as the rules allow this kind of practice the owners will give it a go. Wouldn't be surprised if some rule changes are made sooner rather than later though.
I agree City's model has little to do with sourcing talent.
Re Chelsea/Red Bull. What have Red Bull won? They saved or made money on transfers, great... so what? When they had a genuine world beating cyborg they couldn't keep hold of him.
The model requires letting go of players and constantly chopping and changing. The moment you start building a settled first team opportunities dry up and those attracted by the development focus and moving on to bigger things get turned off/disappointed. Hamster in the wheel.
I think it's a great model for a midtable side that wants to challenge the big clubs ala Brighton or RB. It makes them attractive to young talented players and makes economic sense, but I wouldn't want to see United go down that path personally.
The only clear benefit I can see is that, as someone pointed out, Brexit visa changes could make recruitment of up and coming talent harder. Not missing out and holding certain players for a couple of years while they got enough caps, etc. But then, that's what we used Royal Antwerp for so nothing new, and the likes of Dong never pulled up any trees either.