i think you need root access to go to system\apps.. so it require root..
if somone make the proper update.zip, technically you don't need root. As the recovery mode would effectively boot into root role then patch the system partition(i.e. copy the file, set permission and all those things).
Root your N7 using the Nexus 7 Toolkit (not too far from here)
Copy the Mms.apk to your sdcard folder
Then using the Root Browser Lit (playstore), copy Mms.apk to system/app
Set the permissions:
• Set apk file permissions to rw-r--r-- (644)
• Set apk file ownership to root:root.
REBOOT and you will see your new app :P
[HELP] failed...in attempt to chane the permission to rw-r--r-- (644) it popuped a msg that say "changging permissions was not successful. Please note that some file systems do not allow permission changes"... applies the same in attempt to set the apk file ownership to root:root.
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