It would be great to be able to escape into arbitrary Lua code in a DogTag string -- the same way that a tag currently compiled into a function call, being able to call an anonymous function defined for the purpose would be awesome.

I recently ran into this trying to integrate the Simple iLevel addon: they have a reasonable API that I can use to get at the value, but writing a whole addon to make the tag available, or getting them to integrate it, is relatively heavy. If, instead, I could have added something like this...

[LuaText(SIL:Cache(UnitGUID(unit), 'score'))]

...with unit being the value of the target unit as per the actual tag definitions.

(Alternately, an in-addon mechanism to define new tags through a GUI interface would be equally solid: it would let me set up the same content without having to know nearly as much about building addons.)

PS: I did submit a ticket asking for the sil addon to add support, including my relatively hacky code as an example of how to implement it. Find it here: http://wow.curseforge.com/addons/simple-ilevel/tickets/23-add-lib-dog-tag-3-0-support/