Is it possible, by patch/crack/debug mode... ,to make a medium size city, for example, into a big one?
I built one great city, but I need more space, Is there such an option?

No. You cant. I wish we could...

gonna have to move next door and contuine on from there sadly, no matter what i always start on large

I think it'd be cool to be able to annex another piece of land adjacent to you city for a certain amount of money
Because large is never big enough.