Designing A Linux Distribution For NASA?

Zenker asks: "At NASA we are offering Linux as an alternative to Windows for anyone who wants it. I am working on a contract that puts a new computer on everyone's desktop and we will provide support and services for them. I need to assemble a distribution that will have all the necessary applications without flooding them with numerous option. I don't want to support every word processor and every spreadsheet out there. A good security policy is also necessary. What distribution would you use as a base for supporting a few hundred Linux desktops? Which applications would be standard for your office suite? What would your security policy be?"