Extending existing Project Types - but not all of them

Hi,

I have a folder containing some HTML/CSS/JS-Files.
To treat this folder as a separate project type, I extended existing project types like webclient project which already support everything i want for my new Project Type (refactoring, js unit testing support, etc.)

When i extend that webclient project type with some nodes or option panels, all webclient projects will have those extensions.

This is not intended. i would rather take the webclient project and redefine it under another name, looking for a special file i would put into the project folder. 

I could just copy and modify the webclient project`s code but this seems to be a little too much for the task and i would miss all the updates or would have to merge them into the repo manually.

Is it possibe to re-use an existing project and not influence the behaviour of the original project type - without making a copy of the webclient project?

Thanks in advance for any help,
Nico