Look, I've been doing security work for 14 years. My background is Taekwondo/ Hapkido. I have not trained formally for many years, but the basic standing straight arm-lock, or wrist-lock variation is something I have used on numerous occasions over the years. In my job training, we go over these holds, as well as "come alongs" or escort holds, and hammerlock or shoulder lock variations. We are not encourage to strike, but sometimes it can't be avoided, as it's a natural reaction to hit back when someone hits you. However, If we have to hit, we are encouraged to use open hand strikes, elbow or forearm strikes, and hammer-fists, usually to "green" (non-lethal) target areas which are mostly large muscle groups. As a security officer, our goal is to protect ourselves, our clients, our co-workers and end our shift in one piece not to beat the hell out of someone, "win" fights, or come off looking like a tough guy. We are responsible for the safety of our client, but we also have a responsibility to restrain or detain perpetrators in the least harmful way possible. This is mostly to avoid law suits. Breaking a suspects nose, busting his lip, cutting him open is a sure way to be accused of excessive force and get yourself fired.
So "they" are going to tell you to pursue the current "Flavor of the Month" arts like Krav Maga or MMA. If that interests you, so be it. The best for your professional development, in my opinion are:
Judo
Traditional Jujitsu (Japanese) or "modern" Jujitsu (BJJ ) I would actually steer you toward Gracie Jujitsu.
Aikido (lots of joint manipulations and take downs as well as circular, evasive movement)
Hapkido
There are probably a couple of others, but these are probably the most readily available, and applicable to our profession. Good Luck.
Edit: @ Shadam:
Well, yes, I have worked as a "Mall Cop" , was quite good at it, and had fun doing it. I've also worked loss prevention, and currently work hospital security. If you do your job properly, in a professional manner, you don't have to worry about someone hurting you, because you don't have to fight. When I have had to defend myself, I have done so quite well. I haven't been "hurt" yet; but it can happen to anyone, no matter what kind of skills they have, or percieve that they have. I know what has worked, and continues to work, for me.
As far as you being better at TSD than I am at TKD; you might well be. I have not practiced in years, as I am a hard working adult with a family to support, and little time for recreational training. I don't know what the tournament scene is like these days, but I think 15 years ago, I could have given you a run for your money.
RESPECTFULLY yours,
CM77