That needs dB and since 2.1 dB will be available. Which means that a lot of new things can be added to the script functions, one of them this tag system.
Currently that feature is not even mapped yet. I know what it is and I know why you need it but as far I can't tell you that function isn't on the scoop of 2.X because we are just building the base functions and core system here.
I have taking into account this feature but I don't know when this could be possible made. Most likely, after 3.0