Out of curiosity, I just checked: Via backupmenu's USB mass storage mode(it's a rescue mode app), you -can- change partitions via PC. And, as there is nothing using it, you should be able to safely.
Of course, that pretty much requires a Linux system to do, which is why I want parted ported in the first place...

(also, that's interesting - gparted shows an extra ~64mb of unpartitioned space at the end of the eMMC - was that all there for a safety buffer, or can it be used for a small kernel/bootloader partition or something?)