I think it'd be a tough challenge. From my understanding, Firefox is a heavyweight javascript interpreter, and the rest of the UI and such is implemented in that. You might have beeter luck with something more designed for performance and imbedability. Maybe something based on khtml?
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Stop intellectual property from infringing on me
You know, Opera runs on pretty low system requirements. They don't specify system requirements for Linux per se, but the requirements they list for Windows are quite low. Besides, the browser was designed to be a base for portable devices.