16 is a good age for Grayson. I would suggest the character to be somewhere around 16-18.And that’s why I like the origin of Dick Grayson, those early interactions with Bruce. But I don’t care for the Robin stuff. Yes, they could double down on the strict “you’re not working with me. Sorry Richard but it’s too dangerous. Under NO circumstances” with Dick eventually rebelling and going out anyway. Possibly even saving Batman in his first outing. But that only works if Grayson is like 16-ish. Even then, I still feel like Bruce should and could easily grab this kid and be like “nope! I don’t care, I’m sending you to an Orphanage out of the city if I catch you doing this again”. The fact that he’s willing to go with the sidekick vigilante thing after one rebellious act is...still strange.
The actor can be slightly older, of course.
I think you read too much into the Robin matter, wanting it be treated realistically..
The scenario you describe won't work in our world but we can't look away from the the fact that this is fiction. It only looks real because there aren't anything supernatural or sci fi.