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.