Option to define custom require method or blacklisting strings

I’m using [Nunjucksify](https://github.com/rotundasoftware/nunjucksify) and I have the problem described in this [issue](https://github.com/rotundasoftware/nunjucksify/issues/11). Since I believe plugin runs after all transforms are applied, it can’t know about additional created requires - in the case of Nunjucks, it’s `env.getTemplate({module-name})`.

Is it possbile to have option to define custom require method or option to blacklist particular strings inside requires? That way bundle-collapser will just ignore those modules.