Note: Please don't answer with just use Adobe AIR". I am aware of it, and it's not applicable in this situation.
I've been reviewing the Gecko Plugin API reference.
I'm assuming I'd have to implement all the required browser-side functionality. My goal is to be able to access the graphical output of Flash at a low level, in order to integrate them into an application, along with other native code. Adobe AIR is a future possibility but performance is nowhere near good enough yet for this project.
Does anyone know of an open-source project which acts as a NPAPI plugin host? I suppose alternatives are to extract the necessary bits from WebKit, etc.