Alter the Panelizer Node Task Handler

I would like to have custom contextual links in a panelized node (specifically the edit link to node/%node/edit page). I have found the relevant panelizer code in panelizer/plugins/task_handlers/panelizer_node.inc and have worked out how the handler needs to be re-written to accommodate my requirements. However I obviously can't just hack panelizer so I'm wondering how I should write a module to overide the default panelizer task handler. Is there a hook I can use to alter the plugin or do I have to write a completely new plugin just for the sake of a contextual link?

(I'm pretty much a newbie with ctools/panels/etc. so as much detail as convenient is appreciated, but even a point in the right direction would be of massive help! )