A little more Voxelstein 3D, a little less Minecraft. The shovel and pick could still destroy whole blocks and building should be the same. The gun could destroy the voxels that make up the block instead of the whole thing. I don't even know if that's possible with this game's engine and I haven't put any thought into how it could affect the gameplay but it was just something I was thinkin' about earlier.

Could be a good idea...

What if instead of "breaking", they colourd a voxel black. It would create a bullet hole effect, although, the effect may be lost with the face of the voxel always facing the player.