Pandoc: passing options in config file

How do I pass additional options to pandoc, when a .pdc file is found. I like to set this up in the config file, but can not find an example nor can I figure out if that is even possible.
We need much more than the option --mathjax coded in the source.

How can we avoid creating custom hugo versions with hardcoded options and instead passing them along in a config file.

An example would be real great. Or if you have code that we can put into a pull request to hugo so this becomes documented and implemented that would be great. I am not sure if this is already implemented or not.