[Fire TV Android Development] Skel40:
How to customize your system for both sheldon/p, mantis, raven, etc. You have this important file called the updater-script. This file is way powerful than you realize in terms of what you can do as an example here:

(getprop("ro.product.device") == "mantis" || getprop("ro.build.product") == "mantis") || abort("This package is for \"mantis\" devices
this is a \"" + getprop("ro.product.device") + "\".");
ifelse(is_mounted("/system"), unmount("/system"));
ui_print("NS6297 (With Patches)");
ui_print("Copying system image...");
block_image_update("/dev/block/platform/soc/11230000.mmc/by-name/system", package_extract_file("system.transfer.list"), "system.new.dat", "system.patch.dat");
ui_print("Copying vendor image...");
block_image_update("/dev/block/platform/soc/11230000.mmc/by-name/vendor", package_extract_file("vendor.transfer.list"), "vendor.new.dat", "vendor.patch.dat");
mount("ext4", "EMMC", "/dev/block/platform/soc/11230000.mmc/by-name/system", "/system", "");
ui_print("Deleting efuse burner");
delete("/system/bin/efuse_check.sh",
"/system/bin/ewriter");
unmount("/system");
ui_print("Updating TZ...");
package_extract_file("images/tz.img", "/dev/block/platform/soc/11230000.mmc/by-name/tee1_real");
package_extract_file("images/tz.img", "/dev/block/platform/soc/11230000.mmc/by-name/tee2_real");
mount("ext4", "EMMC", "/dev/block/platform/soc/11230000.mmc/by-name/system", "/system", "");
delete("/system/priv-app/com.amazon.tv.forcedotaupdater.v2/com.amazon.tv.forcedotaupdater.v2.apk",
"/system/priv-app/DeviceSoftwareOTA/DeviceSoftwareOTA.apk",
"/system/priv-app/com.amazon.ime/com.amazon.ime.apk",
"/system/priv-app/com.amazon.vizzini/com.amazon.vizzini.apk",
"/system/priv-app/PackageInstaller/PackageInstaller.apk",
"/system/priv-app/com.amazon.tv.settings.v2/com.amazon.tv.settings.v2.apk",
"/system/priv-app/com.amazon.tv.launcher/com.amazon.tv.launcher.apk",
"/data/system/PackageManagerDenyList",
"/system/priv-app/com.amazon.adep/com.amazon.adep.apk",
"/system/priv-app/com.amazon.aria/com.amazon.aria.apk",
"/system/priv-app/assetsync.service/assetsync.service.apk",
"/system/priv-app/com.amazon.bueller.music-stub/com.amazon.bueller.music-stub.apk",
"/system/priv-app/com.amazon.bueller.photos/com.amazon.bueller.photos.apk",
"/system/priv-app/com.amazon.cloud9-stub/com.amazon.cloud9-stub.apk",
"/system/priv-app/com.amazon.dcpms.fos.service/com.amazon.dcpms.fos.service.apk",
"/system/priv-app/com.amazon.device.sync/com.amazon.device.sync.apk",
"/system/priv-app/com.amazon.device.sync.sdk.internal/com.amazon.device.sync.sdk.internal.apk",
"/system/priv-app/com.amazon.diode/com.amazon.diode.apk",
"/system/priv-app/com.amazon.dpcclient/com.amazon.dpcclient.apk",
"/system/priv-app/com.amazon.ftv.xpicker/com.amazon.ftv.xpicker.apk",
"/system/priv-app/com.amazon.ftvads.deeplinking/com.amazon.ftvads.deeplinking.apk",
"/system/priv-app/com.amazon.gamehub/com.amazon.gamehub.apk",
"/system/priv-app/com.amazon.minitv.android.app-stub/com.amazon.minitv.android.app-stub.apk",
"/system/priv-app/com.amazon.net.smartconnect/com.amazon.net.smartconnect.apk",
"/system/priv-app/com.amazon.ods.kindleconnect/com.amazon.ods.kindleconnect.apk",
"/system/priv-app/com.amazon.securitysyncclient/com.amazon.securitysyncclient.apk",
"/system/priv-app/com.amazon.sharingservice.android.client.proxy.release/com.amazon.sharingservice.android.client.proxy.release.apk",
"/system/priv-app/com.amazon.shoptv.firetv.client/com.amazon.shoptv.firetv.client.apk",
"/system/priv-app/com.amazon.tahoe/com.amazon.tahoe.apk",
"/system/priv-app/com.amazon.tv.alexaalerts/com.amazon.tv.alexaalerts.apk",
"/system/priv-app/com.amazon.tv.alexanotifications/com.amazon.tv.alexanotifications.apk",
"/system/priv-app/ContactsProvider",
"/system/priv-app/DeviceSoftwareOTAIdleOverride/DeviceSoftwareOTAIdleOverride.apk",
"/system/priv-app/sync-provider_ipc-tv-release/sync-provider_ipc-tv-release.apk",
"/system/priv-app/sync-service-fireos-tv-release/sync-service-fireos-tv-release.apk",
"/system/media/bootanimation.zip",
"/system/build.prop",
"/system/priv-app/ArcusListener/ArcusListener.apk",
"/system/priv-app/com.amazon.venezia/com.amazon.venezia.apk");
package_extract_dir("system", "/system");
set_metadata("/system/priv-app/com.amazon.tv.forcedotaupdater.v2/com.amazon.tv.forcedotaupdater.v2.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.amazon.tv.launcher/com.amazon.tv.launcher.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/DeviceSoftwareOTA/DeviceSoftwareOTA.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.amazon.ime/com.amazon.ime.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.amazon.vizzini/com.amazon.vizzini.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/PackageInstaller/PackageInstaller.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/data/system/PackageManagerDenyList", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/build.prop.bak", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/build.prop", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.amazon.tv.settings.v2/com.amazon.tv.settings.v2.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.markus.firetools/com.markus.firetools.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/system/priv-app/com.amazon.venezia/com.amazon.venezia.apk", "uid", 0, "gid", 0, "mode", 0644);
ui_print("Setting Launcher Manager");
ui_print(" by Skel40 ");
set_metadata("/sdcard/emulated/0/lm/lm.apk", "uid", 0, "gid", 0, "mode", 0644);
set_metadata("/sdcard/emulated/0/ATV/ATV.apk", "uid", 0, "gid", 0, "mode", 0644);
unmount("/system");
ui_print("Copying kernel...");
package_extract_file("boot.img", "/dev/block/platform/soc/11230000.mmc/by-name/boot");
package_extract_dir("magisk", "/dev/tmp/install");
set_metadata("/dev/tmp/install/install-magisk.sh", "uid", 0, "gid", 0, "mode", 0755);
run_program("/dev/tmp/install/install-magisk.sh");
run_program("/sbin/mkdir", "/system/addon.d");
ui_print(" Amazon Launcher Replacement ");
ui_print(" by Skel40 ");
ui_print("Forced OTA Bypassed/DeviceSoftwareOTA Patch Installation Complete");
ifelse(is_mounted("/system"), unmount("/system"));

You can choose what apps you want to delete and it can be whatever package whatever setting you want its really easy. Ok open up a file explorer either on android, mac, windows, linux, etc and take this script. Make a folder called META-INF/com/google/android/updater-script which is my updater-script file and use that. make a folder called system/build.prop/, system/priv-app/, system/media/bootanimation.zip and you can adjust it through the updater-script to either add it to system, patch protected system files, like a build.prop. Only use my Patched Roms to extract and please use this system extraction I have to get full customization with the scripted rom development and the updater-script builds the system