Extracting the runtime portion from a minified export is not really doable. I mean at most you could possibly get the minified version of the runtime with a lot of trial and error. Unfortunately all the names would be mangled so it would be a real chore to fix that into a usable form.
To be able to open a capx that uses one of those plugins you'll either have to remove all references like newt says, or you can recreate the edittime portion from the capx. After you unzip the capx you can get all you need to recreate it.
The plugin's id can be retrieved from the .caproj file under used plugins or behaviors.
Next you need to add all ACEs. The event sheet xml stores the id of the action/condition and all you need to recreate it in the edittime is the id and parameters need to be the same. Properties can be done similarly by looking at an instance in a layout xml. just keep the same order and type and you should be ok.
That at least can let you open it. Hopefully your plugins are in an old c2 install somewhere though.