I´ve been becoming a lurker here, and it pains me (life took over), but I do drop in sometimes to watch. Now I have one I immediately feel I can contribute to.
With the Thin Lizzy reference you are of course spot on. Also with your idea for metal though.
Back when I was new here the Emerald bridge was hailed for modern metal dropped tuned stuff. Including the forums own Nolly of Red Seas Fire and stuff (also most of the demo tracks).
Due to the high end and the tight bottom it does work for that style....in certain conditions. That is imho why BKP does not list it as a metal pickup off the bat.
You know how a lot of a metal amps do that thing where they give you that lovely low end and mid thing with the high end a bit tuned down? Even a bit mid scooped? The Emerald works with those for modern metal like a charm (assuming the guitar is not ways off and if your RG is somewhere in the middle field it should work).
A classicly voiced amp will produce classic tones, from Lizzy to 80s hair metal and up, but never modern. Modern sounding amp and drop tuning though....a machine.
On top of that, in the right conditions it will nail the sound while setting itself apart through character. A certain spark of the origin times of modern metal. I love that myself.
So, in short, yeah, the Emerald can work for that. Can, but may not. Depends...