Answering the title of the topic: yes, I do plan to add new features. In fact I update the generator with new features every month or so.
About population: technically it's not hard of course, but it's kind of complicated conceptually. If you need finer control over the city size, you can specify it using the size parameter in the url of the non-itch version like this:
http://fantasycities.watabou.ru/?size=18&seed=333106443&hub=0&random=1