I have mekanism in quite a large pack, and there are tons of things that shouldn't be able to be moved with the cardboard box.

It would be a lot easier for me to make a list of things that should be able to be moved than it would be for me to make a list of things that should not be moved.

I would suggest perhaps removing the use on "any block". Machines, tanks, chests, etc yes should be able to be boxed up, but random blocks don't really have a need to be "boxable".

I'm curious though as to what kind of things you had in mind that would be "unboxable"

The intended behavior of the box is to be able to pick up and move any block in a Minecraft world - this could be anything from a block of dirt to a Mekanism energy cube. The blacklist is the best way to accomplish this.