Wood chips in the barrel seems so easy to try I almost feel like it can't possibly not have been tried before and proven not to work.
Might be something along the same lines as the brewing temperature/ timing of coffee (replace wood surface area for temperature)- hotter water extracts everything faster, but some things faster than others. A longer but colder brew will extract the hard-to-get compounds in larger relative proportion.
Chipping barrels with toasted chips is extremely common in distilleries that are just getting started. Also, smaller barrels and artificial heat/cool cycles. Take some distillery tours, you'll learn a lot of shortcuts to producing passable products.
Oak is used in winemaking to vary the color, flavor, tannin profile and texture of wine. It can be introduced in the form of a barrel during the fermentation or aging periods, or as free-floating chips or staves added to wine fermented in a vessel like stainless steel.
Might be something along the same lines as the brewing temperature/ timing of coffee (replace wood surface area for temperature)- hotter water extracts everything faster, but some things faster than others. A longer but colder brew will extract the hard-to-get compounds in larger relative proportion.
Just rampant speculation though.