I've been trying to code this myself, currently my idea for type three is that it has the properties of reinforced glass powered and unpowered and only the appearance changes, mostly just for a camouflage effect.
I have type one almost done but block below it don't receive the correct light amount. It acts like glass in that mobs still catch fire yet is casts a shadow(glass doesn't cast a shadow). I did get it to allow redstone and levers to be placed on it.
Add a few typed of switchable glass.
Type one: Glass under normal conditions, but when a redstone signal is applied (or eu) the glass turns opaque. This could be used a a roof that sometimes allows sunlight and when powered blocks sunlight.
type two: similar to type one but when powered instead of being simply opaque it emits light like glowstone or redstonelamp. If you use these on a roof you could have sunlight during the day and torchlight at night from the same block. Could be used in conjunction with a block that emits a redstone signal when it detects light to automate the switch from glass to lamp.
type three: This block is similar to the first, it is glass when unpowered but when powered changes to a specific block. It would have a GUI and one storage slot allowing the user to input a target block. (an alternative idea would be that it picks one of the surrounding blocks to mimic). This would allow for a wall to sometimes be glass and sometimes be grass/brick/etc
type four: one way glass, see through on the side with the lower light level, and opaque on the side with more light. if the light is even then opaque on both sides.
