I registered an account just to say thanks for creating this, and also to point out that I managed to successfully edit both Android and iOS FF9 save files using this program.
Running Android, the .dat file is pretty easy to find in the following directory (which you will need root in order to access): DeviceStorage\Android\data\com.square_enix.FFIXww.android_googleplay\files\EncryptedSavedData\SavedData.dat
In iOS it's a little trickier. You either need a:
A) Jailbroken device (in which case you can find the .dat file in the app package under <app>\Documents\EncryptedSaved\)
B) Device running an iOS version between iOS 7.0 and iOS 8.2 (inclusive).
7.0 is the earliest iOS version supported by the game and in iOS versions up to (and including) 8.2, you can access app data without jailbreak through a program like iFunBox (under <app>\Documents\EncryptedSaved\).
My main iPhone and iPad are both running 9.3, so I couldn't jailbreak or access app data. I managed to track down an old iPad running iOS 8.1.2 and got FF9 set up on it with my iCloud account. After that, I downloaded my save file from the cloud to the old iPad, pulled it off the device with iFunBox, edited it in Memoria, put it back on the device, and uploaded the edited save to the cloud. Once the edited save was in the cloud, I could pull it back down on my main devices and load it like normal. Note that you'll need to load the save file from the save slot rather than just hitting the "Continue" button on the main menu; the auto-save loaded by the "Continue" button is not the one you edited in Memoria.
Hopefully someone else will find this helpful. Older iOS devices can barely run FF9, so prepare to deal with a lot of app crashes and just be persistent.