Seen this mod a few times. Definitely keeps people out of your case. However most cues are not stolen due to being taken out of the case, they are stolen when the cues are already out of the case.
Once upon a time I did a case for Oliver Ortmann. The reason I got the chance to do one for him is because his previous case and contents were stolen. So I did the case and installed a motion sensing alarm in it. When set the alarm would shriek loudly if the case was moved.
He used it once leaving his case under a pool table. Someone kicked the case accidentally and it sharked the whole pool room. He never turned it on again.
I think everyone should lojack their cues and case somehow. Then at least if it gets heisted you have some chance of locating it.