No offense but...I have a MUCH better suggestion for sorting your cards.
In Gatecrash, as in Return to Ravnica, it's unlikely that "traditional" allied color pairings will be relevant, so there's absolutely zero reason to maintain the typical color pie arrangement. In fact, due to the guilds, there is essentially a "new" color pie in each of these sets, with different allied pairings representing the guilds.
In Return to Ravnica, this was very easy: just switch the positions of red and black, so that going around clockwise, instead of W-U-B-R-G, it's W-U-R
-G. Voila, you've got WU, UR, RB, BG, GW in a nice color wheel.
In Gatecrash, due to only two traditionally allied color pairings, it's a little trickier. There are two options:
1) Switch blue and black; switch red and green. Going around clockwise, now you have W-B-U-G-R instead, giving you Orzhov-Dimir-Simic-Gruul-Boros.
2) Drop white to the bottom, in between black and red. Now instead you have U-B-W
-R-G, giving you Dimir-Orzhov-Boros-Gruul-Simic. (This is probably what I will use...as I kind of like the idea of Orzhov subverting white's ideas of order, and Boros overdoing white's ideas of justice. :P)
Pardon the horrible MSPaint drawing, but I went ahead and made a graphical representation:
Note that this leaves the center space open for cards that actually belong there, like (non-guild) artifacts and the one colorless land.