Default [Q] Upgrading Firmware by cp -ax?

Hi,

I have a Samsung Homesync running Android 4.4.2. This uses the same HW as Nexus 10, based on Exynos 5250. Both are produced by Samsung. Homesync uses Odin, while Nexus 10 uses fastboot to flash stuff.

Homesync is deeply locked up. I was recently able to root it using saferoot and an updated superuser.zip from Koush.

Despite all I've done on Build.prop etc some apps are still not compatible with Homesync and some apps are not running correctly although they run fine on the Nexus.

Since the bootloader is locked, I was not able to flash anything custom on this, but I got this crazy idea to upgrade the Homesync ROM using Nexus 10 system.img, by simply mounting the raw system.img (extracted sing simg2img) to Homesync, deleting all what's inside /system and then copying the contents of this raw system.img.

One issue I could face is the kernel. Both firmware will be based on 4.2.2, so I'm not going to flash a new kernel and I can also keep the modules as-is if I find any in the original /system directory or /lib/modules.

Would the Touchwiz enabled kernel run Nexus's firmware as well? Or is it too far jump?

I can also try flashing the kernel (ie boot.img?) using dd but I'm not sure if the flash chip would let me do it even when I'm root.

Any views? Hints? Advices? Did anybody try something like this before?
What about the /data partition, would it matter what's inside?

For the cache, I intend to wipe cache & dalvik cache just after replacing /system with the original recovery.