Semi transparent voxels

Sometimes I miss a way for adding details for actual textures without using a lot of entities. Would be possible adding semi-transparent voxels? Similar to the bamboo texture but with much more transparent holes.

Imagine I want to dress a castle wall and add it a touch of randomness. I can use ivies, put inside some small roots, etc. If the wall is huge, that means a lot of entities.

What about a new voxel! The semitransparent roots! Or… the semitransparent moss/ivy/green-thing-that-grows-in-the-wall? Or maybe a spiderweb voxel? Or dirt? That way, extracting it and putting it inside, we could add a lot of customization to different places and make our games more detailed and different.

Not sure if I have explained well but this would be like a png-voxel texture or something like that.