I've read a couple of things recently that have pointed out that all RSC productions of Doctor Faustus since like the 1960s have framed the Helen of Troy scene as a depiction of whatever counts as sexually transgressive for the time/place, so Helen has been represented as a beautiful cis woman but, like, with full frontal nudity; a reanimated corpse; an empty wig and dress which get used as props for a wank session; a man in a dress; and a creepily young-looking girl (played by an adult actress) who is then implied to actually just be a real, normal person who gets murdered in a fit of insanity (?)

Anyway I kinda think this is off the mark not so much because ~good taste or whatever (although pretty much any assumptions regarding what actually counts as transgressive or taboo will probably go to some pretty gross places--if Faustus wants to shag a man in a dress, more power to him) but because I'm not sure how well the scene works if it doesn't also seduce the audience (you can pull a reveal on them later if it suits, but I tend to think the arc of the play as a whole works better if we get closer to Faustus over the course of it, rather than further away, and if his ultimate fate feels somehow unjust on a gut level even if we understand the theological reasoning). And while it's common to read Faustus' embrace of Helen as the thing that seals his damnation, I don't think it is, I think looking for one point where it becomes too late for Faustus is misguided and that it only works if it's either always too late or never too late for him. All the tension of the play hinges on that paradox.

That said, depending on how your lead actors play the central relationship and how quickly you escalate the sexual tension, you can always pull the "it was Mephistopheles all along" variant, which is always a crowd-pleaser.

(It's me, I'm the crowd)