There is definately a simpler way of doing this. You could have 2 levers, one on each side. Both are hooked up to an X-or gate. This means that you can open it on one side then close it on the other and vice versa. Then you put the output of the X-or gate to an invertor that connect to the door. To lock it, simply put a piston transistor on the wire out of the x-or gate and wire that to a lever. I believe this would take up less space, and it would only use 1 piston and 2 levers versus the 2 pistons and 4 buttons you have. Also, never doubt your skill in redstone, a pro always starts from somewhere :D