Change system mount points [Stock ROM]

[Guest bezo999]

Hello.

I will try to be brief. I really love Acer Breeze UI, so I am still using 4.000.13 fw. Recently I am dealing with low capacity by symlinking | .apk-s .dex-s and folders of app's data | to sd-ext partition. But for many reasons, it is not the best solution.
I decided to change /data mount point direct to external SD partition.
As stock ROM does not support init.d, I would like to ask, if it's not possible to -> decompress boot.img -> edit ramdisk's init.rc file with following:

# mount mtd partitions
    # Mount /system rw first to give the filesystem a chance to save a checkpoint
    mount yaffs2 mtd@system /system
    mkdir /system/flex
    mount yaffs2 mtd@system /system ro remount
    mount ext2 mmc@external /data nosuid nodev ???errors=continue # instead mount yaffs2 mtd@userdata /data nosuid nodev
    mount yaffs2 mtd@cache /cache nosuid nodev

Also(for better performance): 

# create dalvik-cache and double-check the perms
    mkdir /data/dalvik-cache 0771 system system
    mount yaffs2 mtd@userdata /data/dalvik-cache nosuid nodev # added
    chown system system /data/dalvik-cache
    chmod 0771 /data/dalvik-cache

I have no idea what "common options of filesystem", I have to use.

So if I do following and compress back to boot.img, than flash to boot partition, will I have all my data on ext SD and dalvik cache on nand partition?

If someone have knowledge about that I do not have, but I try to do it, please devote me a little of your time.
Thank you in advance.