BTW #1
Elsewhere you might read about the reasons why the sdcard is the only inherently writable device.
Rumor has it that the OS folks know the external SD are FAT formatted devices without any user security.
Eventually OS 4++ or 5++ will be multi-user or multi-login and then the devices will need to be NTFS or similar to NT, Vista,Win7 etc so the SD card can have content written to by two or more users yet kept secure.
Meanwhile for 99% of users, buying any external media is a waste of money.
BTW #2
A scarier edit to the xml files is to switch the sdcard and the extsd card identities, so if you bought an android with 4Gb you could theoretically copy all the sdcard files to a 32Gb card, rename the relevant lines and then reboot.
Your android wakes up to find sdcard is now 32Gb I wont be going there - its a scenario to brick the tablet if you make a mistake.