One obstacle we've been working on is a simple switch-gate mechanic. Rather than go for a typical gate, we decided to steal liberally from Kirby and have switches that destroy clusters of blocks.
|It looks like this!|
|Even crazy stuff like this!|
You end up with an attractive cascading effect (which will look nicer when we have real animations and not my ugly ones!) and a flexible system that can be used to create destroyable terrain of all sorts of shapes.