Because I want to.. isn’t that enough?

I have the attribute syntax working, I added a few things besides the string, python and path namespaces things like this are possible:

<div tal:define="attr1 js:object.method(arg);;;
                 attr2 groovy:5;;;
                 attr3 python:object2.method(arg2)" />

The groovy, js and python namespaces are the names of python ScriptingEngine, that means you can use freemarker, javascript, groovy, python, ruby,  PHP, or any engine that supports the JSR 223.

I hope to finish it in a couple of weeks (I only have time to work during weekends)

If you want the check the code, it is here:  http://github.com/iamedu/Dragon-Templates