I bought a Rockshox Reverb Stealth dropper post before I realized that there isn't a way to internally route the remote cable. For the rear shock internal route, I have a remote hose going through it already so no go there.

I'm considering drilling into the down tube to route the cable internally. I came the post linked to below. Is this a crazy idea? What are the ramifications of drilling into it?

http://www.peterverdone.com/?p=7163

Huhu, well, it's your frame, but I doubt you'll find many folks aside from the guy who wrote that blog post saying it's a good idea. The ramifications are you've got no idea how much stress goes through that area, and cutting out a hole interrupts a whole bunch of carbon fibers, possibly creates stress risers, all that fun stuff. But hey - what's the worst that could happen, beyond a crack forming in the down tube where it attaches to the head tube, which would probably lead to catastrophic disconnection between the head tube and the rest of the frame? 

Are you running a 1x drivetrain? Could you drill out the stop for the front derailleur instead of putting a hole in the frame?

I'm running 1x11 XT so front derailleur stop sounds like the safer option. Anything have experience with this?

If the holes stops are in aluminium you can drill them. They are very soft.
I did that to drive the hose until the rear dérailleur end to end.

To drill in the right direction, you can use a small drill first, then increase it mm by mm or so, until you get the wanted diameter(hose+0.5mm).
Or if you are sure to get it right oriented, go directly with the last drill.