Today, A XDA developer (updateing) just Ported Android Nougat 7.0 AOSP for OnePlus One. OnePlus One is one of the most popular devices and is loved by developers. The AOSP 7.0 Build for OnePlus One has only few bugs.
You can Download the AOSP build from XDA Developers and can Install it using any Custom Recovery. This is an experimental build, so it might contain few bugs but according to the developer most of the features are working just fine.