Thanks !
I think I can't automatically generate the plugin. Connect I/O use "nodes" and each node has its sockets. But I can't create custom sockets type, for example, for passing a ReferenceFrame object, I need to make a "ReferencePool" which contains all objects (execpt string, int, etc) and passing the ReferenceFrame with a ID. Then the node using this ID get the object from the ReferencePool. It's quite annoying.
I saw I can open the Connect I/O solution in Visual Studio, and then maybe I can modify the software for allowing custom data, I need to check if it's possible. Thanks for the info !