Two things I could imagine very well.
1. Some nice grey denim. Either something with a really neutral tone or two different models, one with a cold grey and one with a warmer tone.
2. Slim chinos/khakis are quite big now. I could imagine a 16oz superblack material used in a really classic plain front chino cut.
Asp, are you talking about doubling up on the 22oz material on the front part of the legs? I just got a pair of 634SR (awesome). Doubling up on that would definitely yield something that is too uncomfortable and unpractical for normal wear. Sure, if you're a logger or blacksmith, then maybe. But chances are you'd wear leather as a blacksmith and something kevlar reinforced as a logger.
Nice forum, by the way!
Cheers,
Till