Apparently it has already been done.
I'm not sure if I like it though, and keep in mind that it is not anything that is required for you to do, but Logo-Loc is an official partner and it is just an idea of some merchandise available to you..
http://www.logoloc.com/first/teamFIRST.html
I personally don't like how the "05" is in the back (meaning 2005), because of how it makes me think I am on team #5 when I wear it. Not that there is anything wrong with team #5, but if i have something that says Team X, I want it to be my team number. Just a thought.
edit: By the way, Logo-Loc is just recycling the tried and true clothing of sports that were mentioned and adapting it to FIRST Team gear.
I do like the idea of making a brand new standard if for nothing else, then just to say we did it, of a FIRST uniform. Good question.
I would like to think (being mostly on the mechanical team - and having a lot to do with the building aspect of the robot) that a FIRST uniform would mainly consider something that can be easily cleaned, and something with pockets for tools, or a scale or a micrometer/calipers such as a work shirt and a pair of pants, and/or a toolbelt..
But, that is just me.
I still do think that the individualized team gear of all FIRST teams are great things, and I love to trade a shirt for a shirt.