Don't want to be the prototypical middle brow dismissal but this sounds like a bad idea to me. Or it would need to be 100% implemented in the guts of the language. Why? Because strings need to be pickled, memcached, passed to other machines using other languages ding other work, etc.

There was a template language called ptl in python using things like htmltext and it is actually a crazy dog biting everything's and everyone touching it.