Hmm...

Nintendo did actually make a disk for the 64, it was the Nintendo 64 DD (Disk Drive), thing is, like most videogames, the Japenese were the guini pigs, and the N64DD didn't sell well, so it was discontinued. FFVII was already in production and was planned for the N64DD, but since the N64DD didn't make it, FFVII was made for the PlayStation. FFVI was scheduled for a remake many times for the PlayStation (a 3-D version FYI, and if you dig deep enough you'll find that they've got plans for a FFV and FFVI DS).

EDIT: This M-Tek armor monster might be for either the PS version that was discontinued, or for the DS. (I'm still speculating on the DS though. )