not a bad start. The part where you talk about having double doors and only one door can be opened after the first is closed is called a man trap. You could also go more into depth on How you would secure the room itself, for example, I know of some data centers employ Bullet resistant and fire resistant Drywall. they usually use two sheets of 5/8 laided over top of each other for extra thickness. Also you could discuss the use of Fire surpressant systems, to put out a fire. I know some comanys use fm-200, or halon(sp) to put out fires.
The placement of UPS's is important because you just don't want anyone bumping into the Load off button on those puppys Not sure if you mentioned it but alway use steal doors. Then there is just alot of stuff you could get into about biometrics.

The facility that I work in uses multiple layers of physical security to cut down on unannounced guests and tailgating. To get into the building you need a keycard. This leads to a mantrap, where a security guard sits and checks credentals(sp). As we discussed before the next door can't be opened till the first door is closed. The security guard sits behind a bullet proof glass window. the next doorway contains A facial scanner, from there there are individual cages which must be opened via thumbprint and keycard scanner. these cages and doors have dual locking mechinisms(sp) so one door can't be opened till you swip out, ex. you thumbprint and swip to get into cage, you pass your card to someone esle to let them in, but it will not let you pass till you swipe out of the cage that you are in, if that makes any sense.