Being the new guy here I'm hoping I can add to this discussion on two fronts, first and most importantly, getting the x100 series firmwares to work in our x000 units, and secondly how pioneer sees the whole support of older head units issue.
First,
From reading the fail overflow blog I think I have a pretty good idea as to why both he Bluetooth and idatalink issues are happening when a x100 series update is applied to a x000 unit.
It seems it may be related to the devices being mounted by the android OS.
Failoverflow lists the devices of the x000 firmware as follows.
/dev/t