(Note - In regards to anything i say about NOMEX work shirts, I am meaning using or getting the NOMEX work shirts for Operational Use)..
In regards to the work shirts, (Nomex, like MFS) - Ithink it is an option to look at, for wearing at Grass fires and RCR.
For example, you would have your PBI or Nomex Pants, and the work shirt for the above mentioned jobs.
That is a way of getting around having 2 sets of gear (for those with PBI) , as you cant wear your full PBI set at grassys - but with a Nomex work shirt, I think it would be okay.. Otherwise you would cook.