Hut contents

I'd like to change one of the items now available by way of a Hut.  I'm able to change the units that can be found, but can't find
anywhere that specifies that you can get a fullblown city from a hut.  How can I disable this option?

Also, I see that in 2.0+ you can require certain buildings in order to be able to build units.  Is anyone working on a ruleset to
utilize this?

Thanks,
Brian