like below fixes the issue Editing vendor files is a bad idea. If you for some reason HAVE to edit them, I would recommend forking the package and edit in the forked version, then update the composer file to pull the package from your own fork instead. But I would not recommend doing this in a case like this. Instead you should publish the package config file and change the model that it should use.
around this issue You can extend only one class in PHP. However you could create trait and put there functionality from Basecontroller and to use this functionality simple add use Traitname; to class that needs that functionality