The schools are already Tiered to make it difficult to make a top of the line triple tech'd item as it is without specializing. Bori, as a 100 Blacksmith can make a triple tech'd mithril 2 hand sword but needs a Tier 4 shop,jewelry and buffs to do so. If and when they do introduce the Tier 6 items I can see that he has to specialize in weaponsmith to be able to go any further in this craft.
So, leave the skill caps as they are. To raise them now would do little to improve the game but may drive many away.
This whole discussion is based on the upcoming changes to mithril and the fact that they are making it an alloy. However mithril does not exist in the real world so any claims that it should be "pure" and left unalloyed is based soley upon literature. If they decided to change the name from "mithril" to "lirhtim" then the argument that it should be pure is moot.
As far as the other point where metal workers have it harder then other classes this does not have to be either as long as the experiance is based on the number of resources used. So a person making a yew board would gain half as much experiance at the same level as a person making a mithirl (or lirhtim) bar.
As an added, you cannot "Power level" a craft as you can an adventure class unless you have somebody feeding you the raw resources like a high level adventurer feeds you MoBs. You still have to mine,process,decon to make any headway. Some resources, due to their proximity to a player built machine are easier then others but rather then changing the formula just insure those resources have the same proximity to a machine. We have been asking for a Channeller near the swamp for a long time now.
This is not the Forgotten Realms where Mithril is mithril, otherwise silk would be harvested from silkworms and not plants. The change to an alloy was inevitable due to the steel and cobalt precessing the mithril and I would expect adamantium to be the same. As long as the experiance gains are equitable versusone resource products I do not mind in the least.