Personnally i really like mountain base , even if I don't have enough time to develop mine : I think it's really more interesting to adapt your base to a small-size environment with heavy constraints than to make a wide base in the plains.
Concerning your base , in my opinion if you have a mining entrance it's really better to build everything you can inside it : in your case you can make place outside by building Ore Smelters , Hay Stack , Bread oven , Stamp mill inside. With ore/lime boulder inside , one less house (why two ?) , less field (with more fertilizer

) , I think there should be enough place for a better defense.
The only "unfixable" thing i see is the (huge) lime pit , which will probably prevent you from adding more brick wall (either a full second layer to protect even more the center of your base or some inside walls to split your base in several compartments).
Bjebr