Mount sdcard partition as /data
I have done the exact same thing in the past with a Samsung Galaxy Y DuOS S6102 by replacing all the mount lines concerning the data partition in the init scripts and fstab file. 

I couldn't find better solutions (think as future-proof) for the problem because once you look at the boot process for a generic Android device in Wikipedia, you'll notice the kernel runs the init scripts which makeup the directory tree and mount certain stuff that lay the foundations for Dalvik/ART runtimes to kick-in.

So by making a few tweaks to these scripts and partitioning the 8GB SD card into 1GB and 5.6GB, I was able to make it work boot.

Note: The device I used runs on ancient technology with little security features as compared to modern techniques. Hence, you might wanna be careful before making changes.