By just staying with team numbers or names & team logos you can streamline your mfg. and then easily avoid the whole "FIRST" issue, while still providing something cool for the pits.
Something light-weight that can fit safely on the typical pit sign ploes, or hang from curtains would be ideal.
What kind of power supply(s) do you have? Can the signs be battery operated easily? What kind of fonts are available? I think someone already asked, do you have any examples? Sorry we missed checking your sign out at MARC!!
Sounds like a cool idea, keep up your enthusiasm!