Renaming materials is a common enough job that there are several utilities that can do it.

Even a good file editor should be able to do it. They're big files, but a global search-and-replace un on a material name on a .obj file will do it.

You have to be careful about possible filename-matches in a .cr2, but it looks as though the material names only appear once.

I've never really gotten anywhere with the UV mapping abiities of modelling programs--I have a copy of Hexagon, but I use Wings3D--there's a range of possible tools. You've missed a couple of tricks with the airfield terrain model.

1: The model can be split into two materials, the background/sky and the ground.

2: If the materials use two texturemaps, they can share the same UV space.

Looking at what you have, and the reversed normals, I do wonder if you just took two surfaces of a cube primitive. It would explain the huge gaps in the UV space.

I've come across references to Corsairs and Hellcats being tested as torpedo carriers, hence the picture. This is my attempt at a late-war Mk 13, which could be dropped from an incredible 2400 ft and 410 kts. They must have used a fighter to test at that speed.