I personally love playing in mountains or under the ground.
I would love to see that you are able to place ALL blocks inside of mountains.
[Minute 0:47] http://www.youtube.com/watch?v=Ryzx5sqs5J4
Epic battles in an epic environment.
At the moment, there are totally too many restrictions that prevent some real nice creative stuff.
Hopefully, you agree my with my suggestion

All the best,
Soprah