Well, it looks like without some remapping, the F7 is going to stay clean. That being said though, Here's a quick attempt which begins to reveal the issues I'm talking about.
Before I make my amateur critique, I want to say that the model itself is beautiful, hands down. It's well constructed and I can see myself making more F7s in the future.
But, there are a few quirks of the mapping which don't lend itself well to weathering/rusting/'dirty-ing'/etc that I'd like to point out and perhaps suggest a solution to in the name of constructive feedback for modelers.
First off, several parts of the locomotive I find are mapped to small 'blocks', which take the texture and stretch (or tile)it over the section of model it's attached to. If a weathering affect were to be attempted on these parts, they would stick out rather badly, specifically speaking of the window 'bezels' and the ladders/handrails on the sides of the locomotive. In the case of the window bezels or handrails, I would suggest mapping them to utilize the same area beneath them. It may look a tad strange if you look very closely, but overall would look fine without too much scrutiny. The utilized method works well for adding a two-tone affect where desired, but in some cases (such as doors and window bezels) it would be best to not map them as a break-out.
Secondly, I'm a bit surprised that the doors are mapped separately rather than being laid into the sides of the body as they are when viewed in-game or in a previewer. If they opened or closed that might explain it, but as far as I know these are static and part of the main body. If I were to attempt to snag the part of the weathering texture that is supposed to cover the door and apply it to the actual door texture, it would need to be aligned (no big deal) but could suffer scaling issues; not to mention both rear doors on each side share the same texture (same being true for the cab doors), forcing both sides to be at least somewhat identical, even moreso when you consider that one of the sides is either flipped or mirrored a combination of ways, adding to the difficulty. If I knew how, I'd likely adjust the mapping and place the doors and window bezels in the empty areas of the main texture file. Fewer files to reference (resulting in possibly lower package sizes, thus less potentially wasted server space) and ultimately it would be easier to create a texture for.
Thirdly, I noticed something a bit strange with the f7's main texture specifically. The upper hood/windscreen portion is mirrored. Reference the ladder shadow shading in the .tga with how they appear in-game. However, the lower section is not mirrored. I'm not entirely sure why this is, but I assume it's perhaps a bug or oversight. If one were to apply the hazard stripe texture all the way over both halves, you can imagine the adjusting nightmare that could potentially be. Another oddity is the way the a-pillars are handled on the cab. In the texture file, the last two pixels on either side of the a-pillar are stretched around the corner and to the end of the area at an angle, yet the rest of the face of the locomotive is mapped completely. I say this is strange because the texture file has plenty of room for the last section to receive it's own mapping. Again I'm assuming it's an oversight but I wanted to mention it no less.
That being said, though, I still do like this locomotive very much. I like to provide constructive feedback with the hopes of better and more detailed assets being created.
If you sat through all that, here's another green color I stumbled across if anyone wants it. It struck my eye as a nice color.
