A slight Problem you may run into is the keyboard player when it comes to metal.

It can be done but will probrably sound too "riff" heavy w/ twin GTR, Twin Bass, and a keyborad doubling what has already been doubled.

Have every one list 3 songs they would like to play. See what is most common and vote. Or if every one has a different song then use what every one listed, find a common band or groove and decide on the song then.