[Android Software Development] mattmanwrx:
So, I couldnt decompile properly (framework files, think I have sense framework installed on my laptop at the moment), but I did get to look at navigation_bar.xml...

.......................................
<FrameLayout android:id="@id/rot0" android:layout_width="fill_parent" android:layout_height="fill_parent">
<LinearLayout android:orientation="horizontal" android:id="@id/nav_buttons" android:clipChildren="false" android:clipToPadding="false" android:layout_width="fill_parent" android:layout_height="fill_parent" android:animateLayoutChanges="true">
[COLOR="Red"] <View android:visibility="invisible" android:layout_width="10.0dip" android:layout_height="fill_parent" android:layout_weight="0.0" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/menu" android:layout_width="80.0dip" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_menu" android:layout_weight="0.0" android:contentDescription="@string/accessibility_menu" systemui:keyCode="82" systemui:glowBackground="@drawable/ic_sysbar_highlight" />[/COLOR]
[COLOR="RoyalBlue"] <View android:visibility="invisible" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1.0" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/home" android:layout_width="80.0dip" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_home" android:layout_weight="0.0" android:contentDescription="@string/accessibility_home" systemui:keyCode="3" systemui:keyRepeat="false" systemui:glowBackground="@drawable/ic_sysbar_highlight" />[/COLOR]
[COLOR="Lime"] <View android:visibility="invisible" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1.0" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/recent_apps" android:layout_width="80.0dip" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_recent" android:layout_weight="0.0" android:contentDescription="@string/accessibility_recent" systemui:glowBackground="@drawable/ic_sysbar_highlight" />[/COLOR]
[COLOR="Yellow"] <View android:visibility="invisible" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1.0" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/back" android:layout_width="80.0dip" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_back" android:layout_weight="0.0" android:contentDescription="@string/accessibility_back" systemui:keyCode="4" systemui:glowBackground="@drawable/ic_sysbar_highlight" />[/COLOR]
<View android:visibility="invisible" android:layout_width="10.0dip" android:layout_height="fill_parent" android:layout_weight="0.0" />
</LinearLayout>
..........................................

so, there are the four lines... I think the first line is the spare on the left, then there is menu (red), home (blue), recent apps (green) and then back (yellow)... You'd need to swap (For Example) the yellow with the red... But, you'd need to do it with the pictures when being pressed (below those lines), then the 90 degrees rotation and the 270... A lot of work... Would be easier to change the source, but dont know if the miui has source available... :)

[above answer is not 100% accurate, it may not even be accurate at all, it is what I'm guessing! :)]