The plugin system, known as the ZIP System, is now working. It's replaced the older plugin manager with a more efficient and reliable system. I recreated the ZPE MySQL plugin yesterday and got it working again. Part of my plans for this include removing some of the features in ZPE, including the MQTT features and potentially the GUI features in ZPE, and moving them to a plugin.
However, there is currently a drawback to these: instead of working like libraries, these simply add the built-in library functions to the general function list. That means you do not have to call libmysql->mysql_connect but instead just write mysql_connect. I am not entirely sure this is how I feel that these plugins should be accessed.
However, it now means that creating ZPE plugins is now possible again.