I love the idea that Siren Charms is some underappreciated gem that will one day be revered as a musical masterpiece

total insanity. The reason nobody gives a shit about it is because it's bland as fuck. I don't think it's bad, as such, but it's nothing compared to any of the albums before it. Even STYE and ASOP beat the shit out of SC. In years to come most people will just forget it exists.
I'm fairly confident you are wrong. If sacrificing your health for a role makes you more likely to win an Oscar, than having a solid, conceptual sounding record is bound to - for better or worse - be remembered as an underappreciated material.
The reason "nobody gives a shit" about SC is that it's not explosive nor controversial enough. It's a great record to listen to, but when you are racing against songs like Trigger or TQP, you are going to lose, and there is no shame to that.
Songs perform differently live to begin with. I voted for the title track and Rusted Nail for example, but what can you do when the band thinks "the" live song from SC os EG? Talk about insanity...
Last but not least, fan votes should be dominated by obscure songs after the obligatory hits. If I could choose Zombie Inc. or Jotun instead of anything off from battles, sc or soapf, why wouldn't I? Not to mention songs they never or rarely played before.
The current Nine Inch Nails tour is an absolute embodyment of fan-service. They played EPs from start to finish, songs which have not been played for twenty years, and they even busted out the single biggest meme song people were 10000000000% sure they will never ever play live.
Anyway, given how it'll be a co-headlined tour with possibly a limited set list, I have serious doubts about this vote.