The concept isn't bad, however some people probably prefer something dressier than a Tee Shirt.
I suppose you could have knit shirts with collars also,but could you imagine though asking someone, have you seen Joe Blow?
Yeah...... thats him over there, he's the one wearing the CCGTCC shirt.
I assume the people who have name tags that are either blank or turned over, DON'T want to be readily identified. What makes one think that they will a] buy the shirt, b] wear it.
If it were mandatory, it would be easier to mandate that a name tag were worn rather than a shirt.