When you have a lot of connected copycats+ blocks and want to (re)texture them, this involves a ton of clicks, especially, when they already are textured (fight click with wrench, then right click with the new block). A wand that would automate this would be a nice feature.

Left clicking a copycats+ block (or the original create copycat blocks) could remove the current texture and then this would spread to the adjacent blocks. Right clicking with a block in your off hand would (re)texture them, also spreading as long as you have enough of that block type in your inventory.

I do like this suggestion. But what we will probably do is extend the usage of the clipboard and make that able to copy/paste states

The main feature would be the propagation over a large group of connected blocks. Imagine having a track bed for your railroad stretching for hundreds of blocks and you can change all of them from gravel to some other material with one or two clicks.