I hate to be the negative guy, so I'll try to address my concerns with these ideas with as much constructive criticism as possible.
I, too, have wanted a landscape Start screen, not so much because I use the phone in landscape much, but for continuity when I back out of an app that's in landscape. I see three issues here.
1. I know that folks want the ability to put a picture behind the tiles, but it just doesn't work in Windows Phone because so little of the background is visible between the tiles. (Windows 8 leaves a lot more of the screen unused, which annoys me because I'd rather have more foreground for tiles than background for pictures.) Worse yet, the background picture actually makes the tiles less usable because my brain has to separate out the foreground and background imagery. (This is more noticeable around the Me and People tiles since they, like the background, have photographic content.) This collision of information is one of things that Metro is supposed to avoid.
2. If Microsoft adds this, they won't do it in exactly this way because of the status bar. By leaving it at the top, you've both changed the number of pixels available for the tiles and left no place for the app bar. The Windows Phone standards call for the app bar to always be next to the Back, Home, and Search buttons and for the system tray (i.e., the status bar) to be at the far end. (Go into email then turn your phone left OR right -- the app bar stays near the capacitive buttons.) If you follow the design standards for those two things, a landscape layout becomes easier, but still not simple.
3. The reason that it's still not simple is that Windows Phone allows more flexibility in tile placement than Windows 8. In Windows Phone, a user can have a tile layout that has no left-to-right straight line by placing a medium tile at the top left, another one half-way down on the right and then continuing downward. On Windows 8, tiles have to be "chunks" of medium tile size (i.e. 4x2 small tiles). You can see this by resizing a wide tile to small in Windows 8 -- the tiles below it don't shift upward to fill the space. This is because Windows 8 enforces a 4x2 (or 4x4) grid so that overflow can move rightward. IF Windows Phone were to get a landscape Start screen, we'd either have to lose the tile placement flexibility that we have now or accept "gaps" when in landscape mode. (I'd be willing to accept those gaps, I think, but I'm not sure how bad they'd be in some user's tile layouts.)
Grouping settings makes sense. There's been a big call for alphabetizing settings, but grouping might be better if done right.
However, the accent color chooser is going to be a problem. From an app development perspective, Windows Phone apps "know" about three special colors: foreground, background, and accent. (Foreground and background are white and black in the dark theme and are reversed in the light theme.) Because apps typically use these colors rather than black and white directly, there needs to be a reasonable amount of contrast among them so that text in any of the three colors looks good placed over any of the other colors. For example, if a user with the dark theme picked a really blue as their accent color, apps showing some important text in the accent color would be hiding it rather than calling attention to it because the dark blue accent-colored text would all but disappear when rendered on the black background.
The buttons in your notification center are way too small for finger use. Below a 5" screen, you cannot accommodate more than five buttons across -- above 5" you can get to 6 buttons. Your four music controls occupy about half of the width of the screen, meaning that you sized them for 8 across -- way too small. Assume 9mm per button with a 2mm gap between buttons to follow the UI guidelines.
The idea of swiping from the top may be a big obstacle. From my critique above, the system tray is located not at the "top" of the screen, but at the side farthest from the capacitive buttons. Thus, it's on the right side if I rotate the phone clockwise. Pivot and panorama apps use the side-to-side swipes to change panels. If your notification center is taking that gesture, existing users are going to have to change the way that they work, which is generally frowned upon.
Overall, my sense is that you're an Android user trying to bring some of the freedom of Android to Windows Phone. (This is my standard observation if someone mentions notification center, quick settings toggles, or file system access.
I agree that Microsoft needs to loosen up a bit, but I do not want Windows Phone to become Android-like. Effectively, that's where Microsoft came from with the old Windows Mobile product. It was the branding for a product that began life as Pocket PC, just as Android is somewhat like a Pocket Linux.
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