"Robert Allison"
2. Fill and level off with an expoy-type mixture. Not sure though what
would be the best materials to use and how strong/durable it would
be.

Coincidentally, I was thinking of doing something like this too. Recently
with the purchase of a wide screen LCD TV, I gutted my entertainment center,
removing some vertical panels that had half lap stile faceframes attached to
them. I need to fill those half lap holes in the shelf level faceframe rail.
The one thing I'm concerned about is colour matching with the existing oak
stile. Can epoxy be colour matched to a certain degree? If so, does it dry
darker than when first applied?