[Xposed Framework Modules] Yuveh:
Wow, you do know your android OS inside and out!

So I looked into SystemUI.apk/res/values/public.xml and found only 1 match (good news!):

<public type="layout" name="system_icons" id="0x7f04005e" />

Also, I did a search for "battery", "battery_level", "battery_text", "percentage" and "keyguard" just in case, and those are the interesting matches:

<public type="id" name="battery" id="0x7f10015a" />

<public type="string" name="battery_level_template" id="0x7f0a01af" />

<public type="id" name="battery_text" id="0x7f100159" />

<public type="string" name="show_battery_percentage" id="0x7f0a01e9" />
<public type="string" name="show_battery_percentage_summary" id="0x7f0a01ea" />

<public type="bool" name="config_showBatteryPercentage" id="0x7f0c0022" />

<public type="dimen" name="header_battery_margin_expanded" id="0x7f0900a6" />
<public type="dimen" name="header_battery_margin_keyguard" id="0x7f0900a7" />

<public type="layout" name="keyguard_status_bar" id="0x7f04001e" />

<public type="layout" name="status_bar_notification_keyguard_overflow" id="0x7f040058" />

<public type="string" name="keyguard_indication_charging_time" id="0x7f0a0194" />
<public type="string" name="keyguard_indication_charging_time_fast" id="0x7f0a0195" />
<public type="string" name="keyguard_indication_charging_time_slowly" id="0x7f0a0196" />

<public type="string" name="keyguard_charged" id="0x7f0a028f" />
<public type="string" name="keyguard_plugged_in" id="0x7f0a0290" />
<public type="string" name="keyguard_plugged_in_charging_fast" id="0x7f0a0291" />
<public type="string" name="keyguard_plugged_in_charging_slowly" id="0x7f0a0292" />
<public type="string" name="keyguard_low_battery" id="0x7f0a0293" />

<public type="id" name="keyguard_header" id="0x7f10008e" />

And this is in my SystemUI.apk/res/layout/system_icons.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:gravity="10" android:id="0x7f100156" android:layout_width="-2" android:layout_height="-1">
<com.android.keyguard.AlphaOptimizedLinearLayout android:gravity="10" android:orientation="0" android:id="0x7f100157" android:layout_width="-2" android:layout_height="-1" />
<include android:id="0x7f100158" android:layout_width="-2" android:layout_height="-2" android:layout_marginStart="2.5dp" layout="0x7f040050" />
<TextView android:textColor="0x106000b" android:id="0x7f100159" android:paddingRight="5dp" android:layout_width="-2" android:layout_height="-2" />
<com.android.systemui.BatteryMeterView android:id="0x7f10015a" android:layout_width="9.5dp" android:layout_height="14.5dp" android:layout_marginBottom="0x7f0900bb" />
</LinearLayout>

and not really sure what I'm looking for, I figured maybe keyguard_status_bar.xml might be useful:

<?xml version="1.0" encoding="utf-8"?>
<com.android.systemui.statusbar.phone.KeyguardStatusBarView systemui:id="0x7f10008e" systemui:layout_width="-1" systemui:layout_height="0x7f09002f" systemui:baselineAligned="false" systemui:layoutDirection="0">
<com.android.systemui.statusbar.phone.MultiUserSwitch systemui:id="0x7f10008f" systemui:background="@drawable/ripple_drawable" systemui:layout_width="0x7f09009a" systemui:layout_height="0x7f09002f" systemui:layout_marginEnd="0x7f090091" systemui:layout_alignParentEnd="true">
<ImageView systemui:layout_gravity="11" systemui:id="0x7f100090" systemui:layout_width="0x7f09009c" systemui:layout_height="0x7f09009c" systemui:scaleType="7" />
</com.android.systemui.statusbar.phone.MultiUserSwitch>
<LinearLayout systemui:id="0x7f100091" systemui:layout_width="-2" systemui:layout_height="0x7f09002d" systemui:layout_alignWithParentIfMissing="true" systemui:paddingEnd="0x7f0900a8" systemui:layout_marginStart="16dp" systemui:layout_toStartOf="0x7f10008f">
<FrameLayout systemui:layout_gravity="10" systemui:id="0x7f100092" systemui:layout_width="-2" systemui:layout_height="0x7f0900fa">
<include layout="0x7f04005e" />
</FrameLayout>
</LinearLayout>
<com.android.keyguard.CarrierText systemui:textAppearance="?unknown_attr_ref: 1010042" systemui:textColor="#ffffff" systemui:ellipsize="4" systemui:gravity="10" systemui:id="0x7f100093" systemui:layout_width="-1" systemui:layout_height="0x7f09002f" systemui:singleLine="true" systemui:layout_marginStart="0x7f0900a5" systemui:layout_toStartOf="0x7f100091" />
</com.android.systemui.statusbar.phone.KeyguardStatusBarView>

Thanks again for your help! Much appreciated :)