If assassinating the composer is not an option, then tune down. Or get everyone to agree to step up to E. I've played in rock bands for nearly 50 years and I have never once seen a rock song in Eb. So I think this is one of those esoteric and/or rhetorical questions that has no basis in actual usage.
But going with the esoteric for a moment, tuning down on a locked nut tremolo system, like the Floyd Rose II, takes a lot more time than tuning a standard nut. This will also affect action and intonation. So the real choice would be to form consensus and do the song in E.
I wouldn't really suggest assassinating the composer, although that might be easier than down tuning a Floyd Rose II.