Bark, hollow logs, and wood.

I propose adding bark: stripping a log would yield 4 pieces of bark.

Using bone meal or bark on a stripped log would restore it, though the bark would reappear only on the side where the item was used.

The crafting recipe for wood should also be changed (1 log + 2 bark).

Hollow wood could be crafted from 4 pieces of bark.

A standard log would still yield 4 planks, whereas a stripped log would yield 3.
2 pieces of bark could be crafted into 1 plank, and a hollow log into 2 planks.