Whenever I get to the point of adding cams, there will be some on the exterior of my house where I will prob have no choice to run the coax and pwr cables down/across etc. into a hole drilled into the basement where the DVR will be.

What would be the potential results if someone cut the cables and began touching the copper coax with the power cable?

I imagine if I went straight down vertically and drilled another hole into the basement, I could perhaps use some sort of strong plastic tube to protect the cables more. Any recommendations?

metal pipe ..?

Abosulutely EMT(metal) pipe. I always use metal when I'm doing an exterior job, no matter how short the run is, you just never know.

If you don't like dealing with bending metal pipe you could always get flexible metal conduit.