[Moto X Q&A] scryan:
The bootloader variable not supported thing is a little wierd, but doesn't necessarily say its not working...

Did you read through the output? there are only 2 things that actually say they fail, and its pretty straight forward why they say they fail.

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot oem fb_mode_set
...
OKAY [ 0.125s]
finished. total time: 0.125s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash partition gpt.bin
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'partition' (32 KB)...
OKAY [ 0.266s]
writing 'partition'...
(bootloader) This may take a few seconds, if a
(bootloader) different partition table is being
(bootloader) flashed since we need to backup
(bootloader) and restore a few partitions
OKAY [ 0.453s]
finished. total time: 0.719s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash motoboot motoboot.img
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'motoboot' (1604 KB)...
OKAY [ 0.375s]
writing 'motoboot'...
(bootloader) flashing sbl1 ...
(bootloader) flashing sbl2 ...
(bootloader) flashing sbl3 ...
(bootloader) flashing rpm ...
(bootloader) flashing tz ...
(bootloader) flashing aboot ...
OKAY [ 4.849s]
finished. total time: 5.224s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash logo logo.bin
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'logo' (628 KB)...
OKAY [ 0.313s]
writing 'logo'...
OKAY [ 0.844s]
finished. total time: 1.172s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash boot boot.img
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'boot' (10240 KB)...
OKAY [ 0.922s]
writing 'boot'...
OKAY [ 1.315s]
finished. total time: 2.237s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash recovery recovery.img
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'recovery' (10240 KB)...
OKAY [ 0.938s]
writing 'recovery'...
OKAY [ 0.953s]
finished. total time: 1.891s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>mfastboot flash system system.img
'mfastboot' is not recognized as an internal or external command,
operable program or batch file.

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>mfastboot flash system system.img
(bootloader) Variable not supported!
target max-download-size: 768MB
Multi-Flash is enabled!
sending 'system' (262144 KB)...
OKAY [ 16.770s]
writing 'system'...
OKAY [ 7.772s]
sending 'system' (262144 KB)...
OKAY [ 16.710s]
writing 'system'...
OKAY [ 7.627s]
sending 'system' (262144 KB)...
OKAY [ 16.710s]
writing 'system'...
OKAY [ 7.423s]
sending 'system' (162648 KB)...
OKAY [ 10.489s]
writing 'system'...
OKAY [ 4.626s]
finished. total time: 88.174s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash modem NON-HLOS.bin
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'modem' (53804 KB)...
OKAY [ 3.673s]
writing 'modem'...
OKAY [ 2.333s]
finished. total time: 6.021s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase modemst1
(bootloader) Variable not supported!
erasing 'modemst1'...
OKAY [ 0.438s]
finished. total time: 0.438s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot getvar all
(bootloader) version-bootloader: 30B7
(bootloader) version: 0.5
(bootloader) cpu: MSM8960 Pro CS
(bootloader) ram: 2048MB Hynix S4 SDRAM DIE=4Gb
(bootloader) emmc: 16GB Sandisk REV=06 PRV=07 TYPE=17
(bootloader) product: ghost
(bootloader) revision-hardware: 0x8300
(bootloader) radio: 0x3
(bootloader) secure: yes
(bootloader) mid: 026b
(bootloader) serialno: TA643020WW
(bootloader) qe: qe 0/0
(bootloader) unlocked: yes
(bootloader) iswarrantyvoid: yes
(bootloader) max-download-size: 805306368
(bootloader) uid: FD0397040C000100000000000000
(bootloader) imei: 353217051004136
(bootloader) meid:
(bootloader) sku: 000000000000000
(bootloader) cid: 0x07
(bootloader) iccid:
(bootloader) date: 04-06-2014
(bootloader) cust_md5:
(bootloader) reason: Key pressed
(bootloader) ro.build.date: Wed Jun 25 17:01:58 CDT 2014
(bootloader) ro.build.id: KXA21.12-L1.26
(bootloader) ro.build.tags: release-keys
(bootloader) ro.build.type: user
(bootloader) ro.build.user: hudsoncm
(bootloader) ro.build.version.codename: REL
(bootloader) ro.build.version.incremental: 18
(bootloader) ro.build.version.release: 4.4.4
(bootloader) ro.mot.build.customerid: RETASIA
(bootloader) ro.product.name: ghost_retasia
(bootloader) ro.build.fingerprint[0]: motorola/ghost_retasia/ghost:4.4
(bootloader) ro.build.fingerprint[1]: .4/KXA21.12-L1.26/18:user/releas
(bootloader) ro.build.fingerprint[2]: e-keys
(bootloader) ro.build.version.full[0]: Blur_Version.212.44.26.ghost_row
(bootloader) ro.build.version.full[1]: .AsiaRetail.en.03
(bootloader) kernel.version[0]: Linux version 3.4.42-g50861a7 (h
(bootloader) kernel.version[1]: udsoncm@ilclbld27) (gcc version
(bootloader) kernel.version[2]: 4.7 (GCC) ) #1 SMP PREEMPT Wed J
(bootloader) kernel.version[3]: un 25 17:11:41 CDT 2014

all:
finished. total time: 0.219s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase modemst2
(bootloader) Variable not supported!
erasing 'modemst2'...
OKAY [ 0.438s]
finished. total time: 0.438s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot flash fsg fsg.mbn
(bootloader) Variable not supported!
target reported max download size of 805306368 bytes
sending 'fsg' (225 KB)...
OKAY [ 0.328s]
writing 'fsg'...
[b](bootloader) Battery Low!!
FAILED (remote failure)[/b]
finished. total time: 0.594s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase cache
(bootloader) Variable not supported!
erasing 'cache'...
OKAY [ 0.659s]
finished. total time: 0.659s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase userdata
(bootloader) Variable not supported!
erasing 'userdata'...
OKAY [ 0.547s]
finished. total time: 0.547s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase customize
(bootloader) Variable not supported!
erasing 'customize'...
OKAY [ 0.172s]
finished. total time: 0.187s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot erase clogo
(bootloader) Variable not supported!
erasing 'clogo'...
OKAY [ 0.531s]
finished. total time: 0.531s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>[b]fastboot oem config carrier ASIA
...
(bootloader) Failed to flash config value[/b]
OKAY [ 0.156s]
finished. total time: 0.172s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot oem fb_mode_clear
...
OKAY [ 0.172s]
finished. total time: 0.172s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>fastboot reboot
rebooting...

finished. total time: -0.000s

E:\New Software\Moto\XT1052_RETAIL-ASIA_4.4.4_KXA21.12-L1.26_18_cid7_CFC_1FF.xml
>

You need to fix those two failures, it looks like even with the complaint in the other partitions, they flashed. Apparently "ASIA" is not an acceptable replacement for vzn in that second command, you will have to find out what value YOUR carrier is supposed to use.

Hopefully after that everything will be good.