@Xaelath,
Concerning what I mentioned "Whereas words ending with "r" usually uses ル, and I haven't seen a case where they used レ.", I made a mistake, it's only words ending with 'l' that uses ル.
Yes it's the pronunciation that matters. Japanese katakana transcription from English follows pronunciation conventions where 'r' endings are omitted entirely and replaced with ー (i.e. flower = フラワー). Which is why peers is written as ピアーズ.
I am not questioning the slang レズ, I'm just saying the point you brought up does not work. Since the Japanese for vampires would be ヴァンパイアズ, and not what you mentioned "ヴァンピ(レズ)".
Even with peers, it would be ピアーズ and not ピレズ.
レズ just does not fit into the title anywhere is my point. Not unless you were to pronounce it vam pee rez, which I don't think is the correct pronunciation in English or Japanese.