I think the problem with this analogy, though, is that (1) mages in DA are adults and (2) most of them don't have any emotional or behavioral problems and would be fully capable of handling themselves outside the circle. I'm not sure I remember exactly what your workplace is or if I'm filling it in with something similar a friend of mine does, so I apologize if I'm misunderstanding, but to me, the Circle seems more like forcing every child with a family history of emotional problems or life circumstances that might lead to them being categorized as at-risk into a group home, and then forcing them to stay there even as adults, via threats of death or lobotomy.
I also think I need to stay out of all forms of the How To Solve A Problem Like The Mages debate from here on out, though, because the more I think about it the clearer it is to me that if I were somehow teleported into Thedas with magical ability and with both the nature and nurture parts of my real life personality intact, there's a 75% chance I'd be throwing fireballs with Adrian, pragmatic / realistic / compromise-focused problem-solving nature and crush on Cullen both be damned.
From my removed real-world standpoint I'm totally with you on "reformed circle is the way to go" but if I were really there I'd almost definitely be pretty angry and irrational about it unless they got me in there as a babby.
LATE EDIT: That said, I do get what you mean about it not being appropriate to be "friends" with someone for whose safety you're responsible. I'd just prefer something more similar to a commissioned officer / NCO relationship, where it reflects professional roles rather than anything intrinsic to the person, and where, as you mentioned, Cullen would have no problem being close friends or lovers with a mage from a different Circle. That's not a perfect analogy either because IIRC a Sergeant Major still has to salute a 2nd Lieutenant, which would be inappropriate and infuriating in the mage / templar situation, but I hope my meaning makes sense.
Yeah, I really wasn't going for an application this broad when I made my point. I was specifically responding to the statement I quoted, not (for the moment) arguing for or against circles. 
What I was trying to say is that as a caretaker, there are certain boundaries I have to observe. I do work with adolescents, yes, but there are similar boundaries between staff and residents in adult residential facilities also. It's more a function of our role than the specifics of my residents' ages or why they ended up in care.
Whether or not mages should be in circles, that was the situation Cullen was dealing with when he made that statement. In that context, I think the statement has to be understood in terms of those boundaries as well as Cullen's personal feelings. At the time, those were the facts Cullen had to work with, future hypotheticals aside.
For the record, I have close friends with the same diagnoses as my residents... but they aren't my residents. I'm not responsible for their care, and that makes a difference in what boundaries I should be observing. (Again, the analogy is imperfect because being a mage is not a disorder, but it's the best I've got.)
Likewise, there would be a difference between the mages a templar was responsible for and those that (for whatever reason) he/she wasn't. 