It seems like you are describing an oxymoron. It's not possible to create a browser that both supports plugins, but disables DRM. Plug-ins (assuming you are referring to the NPAPI) by definition can do anything they want, and in fact are used today to implement DRM in the form of Silverlight and Flash (RTMPE). Think of this as an alternative <object> tag, that doesn't allow arbitrary plugins, but one very specific to encode and decode audio/video.
Fun fact, if you have used Youtube, you have probably consumed DRMed content via Flash's RTMPE support.
I meant addons and extensions, not native code plugins. I have all plugins including flash disabled, so no, I don't consume DRM content via Youtube or any other site.
Fun fact, if you have used Youtube, you have probably consumed DRMed content via Flash's RTMPE support.