Yes, I know my MS Paint skills are comparable to that of an autistic monkey, but you don't need to compliment me on them.
Well, this is a rant from a real drummer, so sit on down or get out before it's too late.
First, before you make a quip about it being a prototype, remember it's a working prototype, and the game is pretty close to final production. So while the design can be changed before manufacturing, it's likely it won't be drastically so.
Well, the most obvious thing from the picture is the awkward looking design. From the scans, it looks like a set of quad-toms on a stand with a pedal. First off, I can understand why they'd only put five buttons on the design, but the four in a line (and according to GI, uncustomizable) design is the real heartbreaker. It's probably the worst design they could have picked to emulate the feel of a real set of drums short of a vertical line.
A 2x2 square would be a far better choice, as you could simulate hi-hat on the TL, snare on the BL, ride on the BR, and splash or effects on the TR, and it could change in a fly to a standard snare/rack toms/floor toms for fills. I don't know where the crash would go for fills, but my assumption would be crash on the TL and crash ride on the TR for the end of fills.
I'm not demanding there be six pads like in my picture (which I think would be awesome and help the drums stay in synch with the new and more realistic guitars, plus ramping up the difficulty and make difficult beats that span multiple drums and cymbals feel more natural), but I personally think it would be a great addition. They should at least change it to a 2x2 square over a 4x1 rectangle. Maybe even an upside down isosceles trapezoid, which looks like
For the geometrically challenged.
Second off, I know this will change, but currently the drums don't look very aesthetically pleasing. Maybe put a large metal or plastic round in the bottom (a great place to fit that ever important logo) to simulate the look of a bass drum from the front. It doesn't even have to have depth, just be there and look pretty. The drums themselves should look less metal and rubber and more plastic and wood. I'm fine with the metal rack, that's natural.
And lastly, why no double bass pedal? Seriously, it doesn't even have to do anything extra than hit the same trigger the normal one does. It would make faster passages on the bass more manageable, and really, so much more metal than it would be with one.