How is it possible to override the main_template.pt in theme addon? The the is created by "mrbob -O my.theme bobtemplates:plone_addon".
Are you really sure you need to do that (I doubt)?
With diazo you can make 'whatever you want' anyway..
If you really need to do to,
you can probably put it your.product/your/product/browser/overrides
If you dont have the zcml, it would probably be something like:
<!-- Set overrides folder for Just-a-Bunch-Of-Templates product --> <include package="z3c.jbot" file="meta.zcml" /> <browser:jbot directory="overrides" layer="your.product.interfaces.IMyLayer" />
You will also have to have :