matthatter,
I raise a lot of mixed types too. I just prefer Grass Types. I like the fact that Grass is weak to Fire. I love the astonished look on peoples' faces when I annihilate their Fire team with my Grass Team.
Which fossil are you going to choose?
I'm going to choose Amaura! Between its evolution Auroras and its move Freeze Dry (an Ice Type move that's super effective against Water Type), it's amazing!