[Nexus 5 Q&A, Help & Troubleshooting] chopper the dog:
It's an easy edit if you have the ability to de/recompile systemUI.

Navigate to SystemUI.apk\res\layout\navigation_bar.xml. I didn't like reaching over for the back button so all I did was flip recents and back. To do that all you need to do is reorder the lines in the 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">
<View android:visibility="invisible" android:layout_width="40.0dip" android:layout_height="fill_parent" android:layout_weight="0.0" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/recent_apps" android:layout_width="@dimen/navigation_key_width" 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" />
<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="@dimen/navigation_key_width" 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" />
<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="@dimen/navigation_key_width" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_back" android:scaleType="center" android:layout_weight="0.0" android:contentDescription="@string/accessibility_back" systemui:keyCode="4" systemui:glowBackground="@drawable/ic_sysbar_highlight" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/menu" android:visibility="invisible" android:layout_width="@dimen/navigation_menu_key_width" 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" />
</LinearLayout>

The above code shows after the edit that gives me the order of (recents/home/back)

<FrameLayout android:id="@id/rot90" android:paddingTop="0.0dip" android:visibility="gone" android:layout_width="fill_parent" android:layout_height="fill_parent">
<LinearLayout android:orientation="vertical" android:id="@id/nav_buttons" android:clipChildren="false" android:clipToPadding="false" android:layout_width="fill_parent" android:layout_height="fill_parent" android:animateLayoutChanges="true">
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/menu" android:visibility="invisible" android:layout_width="fill_parent" android:layout_height="40.0dip" android:src="@drawable/ic_sysbar_menu_land" android:layout_weight="0.0" android:contentDescription="@string/accessibility_menu" systemui:keyCode="82" systemui:glowBackground="@drawable/ic_sysbar_highlight_land" />
<com.android.systemui.statusbar.policy.KeyButtonView android:id="@id/back" android:layout_width="fill_parent" android:layout_height="80.0dip" android:src="@drawable/ic_sysbar_back_land" android:scaleType="center" android:layout_weight="0.0" android:contentDescription="@string/accessibility_back" systemui:keyCode="4" systemui:glowBackground="@drawable/ic_sysbar_highlight_land" />
<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="fill_parent" android:layout_height="80.0dip" android:src="@drawable/ic_sysbar_home_land" android:layout_weight="0.0" android:contentDescription="@string/accessibility_home" systemui:keyCode="3" systemui:keyRepeat="false" systemui:glowBackground="@drawable/ic_sysbar_highlight_land" />
<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="fill_parent" android:layout_height="80.0dip" android:src="@drawable/ic_sysbar_recent_land" android:layout_weight="0.0" android:contentDescription="@string/accessibility_recent" systemui:glowBackground="@drawable/ic_sysbar_highlight_land" />
<View android:visibility="invisible" android:layout_width="fill_parent" android:layout_height="40.0dip" android:layout_weight="0.0" />
</LinearLayout>

The above shows the same order edited to the "@id/rot90" grouping so that the same order is shown in landscape.

good day.