Smarty as extension

[Note: just posted this in smarty.general, was notified it
would be more appropriate here]

Wow, my inquiries into Smarty Light drew alot more negative
response than I expected.

Actually, in posing the question I did not fully explain my
alterior motives.  My plan was to cut out all the features
from Smarty that I know I would not use, and hopefully in
doing so learn a great deal about the code, and then to
later take a crack at porting this smaller Smarty
into a Zend extension.

Now again, please excuse my ignorance on the topic.  As
I understand it Smarty was originally meant to be a Zend extension
but that proved to be difficult (impossible??) and so it
was written in PHP.
So, if I may ask, are there any showstoppers that would prevent
writing Smarty as a Zend extension, or is it simply a matter
of no one has had the time/need to do so yet? Or, like the Smarty Light 
idea is it simply that there would not be much point to doing so.

Thanks,
Ara Anjargolian