I think skills for logging, mining, and harvesting would be very detrimental. High level characters would run to the mines and chip off a bunch of mythril or darksteel, then make a bunch of ingots with a minimal investment. They would no longer need a fleet lower level people to support their craft, so the now unemployed miners wouldn't be able to scrape up enough money to buy new armor and spells. They would not actually reduce the cost of their finished items, (why make a 50% profit when you can make 80% instead) so the lower level folk would still have to find a way to get cash.
I really like the way that it is set up now. A level 75 character has just as much a chance to get a good item as I do. And really, it doesn't matter how good you are with a pick, if there is only tin in the ground where you are mining, you can't turn it in to silver.
Now what would be nice is if there were better axes, picks, and hatchets that you could craft that break less often. That would rock. Oh, and if pebbles were eradicated from the face of the Vana'diel, that would be good for me also. (Stupid no-good lousy rotten pebbles, breaking my picks and not actually worth anything…)
By the way, all of you miners out there in Bahamut, stop driving down the cost of platinum! I have to make a living somehow- dispel, phalanx, and refresh aren’t going to jump into my lap. Thank you.