1. Holding shift will let you ‘creep’ walk, and not fall off the edge, this helps us build in those tight spots, but it gets really tiring and painful when you have to hold down shift all the time. Why not make it so when double-tapping shift will automatically put you in ‘creep’ walk mode with you having to hold down shift, and when you start running (double W) it will cancel the automated ‘creep’ walk.
2. In other building games, some of them have it where you would just click and hold the right mouse button and it will continue to place blocks, add this into the game for fast and easy way of placing a lot of block in the world, but sometimes that would cause unintentional mistakes, so make it so that you would have to double-click the right mouse button, with the second click you would have to hold it down to initiate the automated action of continuously placing blocks.
Hope this helps.
-FreakOrama