My thinking behind this (as a suggestion or feature request) would be
the ability to still pass the info into your php template file using
$this->template->set('my_age', $my_age);
$this->template->show();
without the need for any include statements.
If the template file is .tpl then process with Smarty... if it's .php
then process it like a php file instead.
This would still allow the separation of controller and viewer without
changing how the code is written, would allow the option to not use
Smarty, and would not 'break' any old code where you wanted to change
from tpl template to php template.
As a side note, one of the features of CodeIgniter is exactly this.
Thanks