I don't see any problem with a piano roll system per se and this one seems reasonably clear to me. Perhaps I'm more receptive since I have seen a lot of Guitar tablature and am used to seeing the notation accomodating the instrument.
Nevertheless, EasyKey seems like a dead duck for several reasons.
1. A piano roll system needs to roll: i.e. be animated, which means that it is no real use for "dead tree editions" of classical works. If this is intended for computer-based scores, I would think that you would have massive problems showing that your system was different enough from others to be copyrightable.
2. A piano roll system works for pianos, but how do you transcribe for other instruments? Even if you had a computer system for transcribing to guitar, it would have to be super-intelligent to work out reasonable fingerings.
3. Standard notation is already being used, so the barrier for entry is enormous. It makes more sense for someone to learn to read conventionally-notated music than to learn on an eccentric system for a mechanical benefit only to have to learn a completely different system later.