Something just makes me feel like this is a bad idea but I don't know why.
The Disc drive is fine as long as he makes sure its sitting properly in the slot. The biggest problem of side mounted drives is the disc falls out during closing.
Put it in properly and it should be fine, we had one like this in the back of the car for a while and had no issues.
Did you have a Mac Pro in your car? On its side or standing up, that should be an interesting story! Or perhaps it was merely a sideways optical drive?
it'll work fine.. people have been using optical drives sideways for like 20 years