I'm still a little confused by your description, but I have a hunch you're talking about plugins that are already a part of the standard SDK download? My ant task already filters out those plugins/features....
> Would be cool if one could automatically run through
>> plugin.xml/feature.xml and look for "evil" plugin references.
>
> I have absolutely no idea what you mean by "evil" ... care to expand a
> bit more? (I'm guessing you mean org.eclipse.emf.*? =)
I mean any <plugin ...> that:
references eclipse core plugins
or
something that is in a feature