Yes, of course, but then I suggest you delete your Harmattan for good if you want to do that See, the reason for having multiple partititons is that different OS'es like to live on their own partitions. Basically Harmattan would also only need one (the root partition) but the home directory is on it's own partition to make it simpler to flash the OS without deleting user data, like in OTA update. The reason MyDocs is on a separate partition is a bit different, that is done so you can export it to external computers as mass memory. That is also the reason it is formatted by default in such an arcane and braindead FS like FAT