It's really hard to find a good singer in Hungary. A lot of person into that "Tankcsapda" named shit, which is a copy-paste band with shitty lyrics about getting drunk etc. Their fans really like to discriminate non-fans (eg. "If someone don't likes TCS, he/she is a poser"). And I'm into prog metal instead of some Motörhead ripoff.
I thinking on using Megurine Luka, as "she" can sing in English. With some trick, Vocaloids can do some screamed voice, but not very well.
I'd never heard of these vocaloids before, but that'd be pretty cool if you could pull it off.