"Collectable" ? Maybe to someone that has a Red Cross Museum or someone looking for something different.
How did you determine (since there are not any Ford records) that this particular car was originally ordered for the red cross? Like many 2-30's roadsters that are restored as "Fire Chiefs" cars a convertible would be impractical especially in much of the country and would not serve much as a purpose as a van, truck or station wagon would
Don't believe that its Red Cross connection if be, would increase the value as its not just about rarity