Problem Loading Extended Library From Third_Party

[eluser]CroNiX[/eluser]
If you extend something, you don't load the extended version; you load the original and CI will automatically load the original AND the extended version. Anything in the extended version that overrides the original will be used instead.

Core Classes (see Extending Core Classes section)
Creating Libraries (see Extending Native Libraries section)

So I don't think you will be able to do this and have it in the 3rd party directory. You are messing with the way CI fundamentally works here and can break a lot of things, especially if you want to use other peoples libraries and contributions.