Of course you need a new bike! (that is the answer you were looking for, right?)
I'm really not the person to talk you out of this, since my new frame arrives at the LBS tomorrow.....
I also can't really address the hybrid vs road/cross question (I haven't ridden a non-drop barred bike other than my old MTB, and that's heavy/geared differently/doesn't fit me very well so not a good comparison to the other bikes), but I can vouch for cross bikes as commuters. My commute is about 2x yours and I've been riding a cross check (which, if you happen to be tall (5'10"+), I'd make a great deal on the wheels/frame) which has been great for hauling stuff but also letting me get down out of the wind when I ride up the river for a few miles. It's also great on mixed-surfaces and depending on my route I mix some gravel in. The only reason I'm getting a new frame is I want disc brakes for rain/snow/muck (and the new frame is glittery purple, but that's just a bonus...).
On the parking question.... are the security guards in the metal detector area the same every day? If so, do you say good morning, etc daily? I might feel ok leaving my (wheel/frame locked) bike in there if I had a good relationship with them and I felt that they knew me/might look out for my bike. Also, what's the foot traffic in/out of your building like? Is it employees and the occasional visitor or lots of general public moving in/out? I would probably be less comfortable if there was a lot of non-employee traffic in/out of the building. Otherwise it's kind of a tough situation, the lack of cover would bother me more than locking outside-- especially if you ride in the rain. I lock mine outside some days (if I get here before security, it comes upstairs and sits by my desk...) and feel ok with it there, it's a good rack, I use a couple locks (one cable, one U), and there are other bikes nearby that are locked less well. My current bike is also boring brown and decal-free, so hopefully less of a theft magnet, good frame, good parts, but less obvious.