I didn't say impossible, just that it will require a lot of work and specialist knowledge, will only give you a little bit of space and unless you are able to shrink the system partition at the same time (depends how big the ROM is, which I don't know for that device) it will cause you to run out of space for apps sooner.
I have repartitioned the internal storage of a phone before, so have some idea of what I'm talking about. But the method I used was specific to that phone model, and didn't try to create an extra partition and redirect sdcard to that, so it wouldn't help you. That's why you need a device specialist.