[Xiaomi Mi Note Pro] Aqq123:
Modifying the System Partition Image (Except Configuration)

Removable Files

Removable Apps

The following apps (directories) can be recursively removed:

/system/app/AnalyticsCore/

/system/app/BaiduNetworkLocation/

/system/app/BugReport/

/system/app/matcli/

/system/app/Metok/

/system/app/MiLinkService/

/system/app/NVItem/

/system/app/PicoTts/

/system/app/SecurityAdd/

/system/app/TrafficControl/

/system/app/VirtualSim/

/system/app/XiaomiVip/

/system/app/XMPass/

If you are using the stock version, you can also get rid of these (in Xiaomi.eu's version, these are already removed):

/system/app/BasicDreams/

/system/app/Galaxy4/

/system/app/GameCenter/

/system/app/GooglePinyinIME/

/system/app/HoloSpiralWallpaper/

/system/app/LiveWallpapers/

/system/app/MiuiSuperMarket/

/system/app/NoiseField/

/system/app/PaymentService/

/system/app/PhaseBeam/

/system/app/PhotoTable/

/system/app/SystemAdSolution/

/system/app/VisualizationWallpapers/

/system/app/VirtualSim/

/system/app/VoiceAssist/

/system/priv-app/MiGameCenterSDKService/

Contrary to some information posted elsewhere, do not remove /system/app/NetworkAssistant2/ or you will get a force-close going through some mobile network settings. Also, while /system/app/Whetstone/ can possibly be removed, removing its libraries in /system/lib/ and /system/lib64/ will cause problems.

Removing Google Apps

Xiaomi.eu already includes a minimal installation of Google Apps but I am flashing a larger Open GApps package later so that the 500+ MiB free space on the /system partition can be put to good use. To avoid any conflicts between the two versions, it's a good idea to get rid of all the pre-loaded Google files first:

/system/etc/permissions/com.google.android.dialer.support.xml

/system/etc/permissions/com.google.android.media.effects.xml

/system/etc/permissions/com.google.widevine.software.drm.xml

/system/etc/preferred-apps/google.xml

/system/etc/preferred-apps/

/system/etc/sysconfig/google.xml

/system/etc/sysconfig/google_build.xml

/system/etc/sysconfig/

/system/framework/com.google.android.dialer.support.jar

/system/framework/com.google.android.media.effects.jar

/system/framework/com.google.widevine.software.drm.jar

And the apps themselves (recursively):

/system/app/CloudPrint2/

/system/app/GoogleCalendarSyncAdapter/

/system/app/GoogleContactsSyncAdapter/

/system/priv-app/GoogleBackupTransport/

/system/priv-app/GoogleFeedback/

/system/priv-app/GoogleLoginService/

/system/priv-app/GoogleOneTimeInitializer/

/system/priv-app/GooglePartnerSetup/

/system/priv-app/GoogleServicesFramework/

/system/priv-app/Phonesky/

/system/priv-app/PrebuiltGmsCore/

Note that I am not deleting /system/etc/permissions/com.google.android.maps.xml and /system/framework/com.google.android.maps.jar as for some reason those files are present in the stock ROM too. I am also keeping the WebView (Chromium) component. The above list can be used with MIUI Pro as well but you also need to remove the camera library that is not part of Xiaomi.eu's distribution.

Removing Other Garbage

MIUI includes the CD-ROM emulation "feature," which we'll be getting completely rid of shortly:

/system/etc/fake_cdrom_install.iso

The following font files are only included with Xiaomi.eu for obscure reasons and are probably obsolete:

/system/fonts/AndroidEmoji.ttf

/system/fonts/DroidNaskh-Regular-SystemUI.ttf

/system/fonts/NotoSansHebrewUI-Bold.ttf

/system/fonts/NotoSansHebrewUI-Regular.ttf

With regard to the latter two files, only some scripts have an UI variant in the Noto Sans font, and Hebrew is not even one of them. These two font files are the same as their corresponding non-UI variants. For some reason, Xiaomi.eu also forgot to include Burmese fonts, which are part of the stock ROMs.

These files seem to serve no purpose either:

/system/bin/qmi-framework-tests/

/system/media/audio/create_symlink_for_audio-timestamp

Modifiable Files

Here are some items that can be updated on the System partition, except the configuration files, which will be discussed separately later:

/system/app/<AppName>/<AppName>.apk

/system/priv-app/<AppName>/<AppName>.apk

If you want to add any extra system apps.

/system/fonts/

The fonts used in MIUI are generally based on outdated versions, and some of the fonts Xiaomi.eu uses are even older, apparently. The versions I am posting as an attachment are the latest at the time I was collecting them, which is roughly the time of this post. Alternatively, potentially newer versions can be downloaded from the following sources: Roboto, Noto (use unhinted, alternative link), Carrois Gothic, Coming Soon, Cutive Mono, Dancing Script, Naver fonts and others.

Note that Xiaomi.eu replaces the default MIUI fonts with Roboto, which is a good idea, as it solves some problems. The collection I posted in the attachment does the same.

/system/media/audio/alarms/

/system/media/audio/notifications/

/system/media/audio/ringtones/

If you want to add some extra audio files, this is the place (use the Ogg Vorbis format). Of course, you can just as well put them on the User Data partition.

/system/media/lockscreen/

/system/media/wallpaper/

Ditto, graphics files in the JPG format.

/system/media/theme/

This is a very interesting place to have a closer look, so I'll write about it in more detail later, with the exception of briefly mentioning the following:

/system/media/theme/miui_mod_icons/

The customized, MIUI-themed icons for all applications are stored here. The stock ROM barely includes any icons, while the collection shipped with MIUI Pro is much larger than that of Xiaomi.eu, so you may want to combine the two in your device's ROM (even more interestingly, many icons for popular apps overlap, and you will have two completely different versions to choose from for each of them).

/system/usr/icu/icudt53l.dat

The International Components for Unicode data. A newer version is available included in the attachment, or download it directly from source (making sure it's in the same format). It appears that the data downloaded directly from ICU does not include some charsets, pending further investigation please do not use this version. It should be safe to use the Google Source version but since newer Android releases switched to a different ICU format, the last version available there is not necessarily better than the one provided by Xiaomi.

/system/usr/share/zoneinfo/tzdata

The timezone data included with the latest MIUI is version 2015a, while the newest (as of now) is 2015g, as several countries made adjustments to their timezones last year. If you want to be up to date, download the newest version from the attachment or get it from the source.