I'd like to see a system where whenever you smith armour or a weapon, there's a chance (increased by your smithing level above the item's level) for it to be a Masterwork (or similarly named) version of that item. What do I think it should do? I don't think a stat increase exactly, it doesn't even need a visual difference, but instead it alchs and sells to shops for slightly higher coin. It stands to reason that a high level smith could, on average, make better steel armour than a lower level smith, and I would like to see grinding out steel or mith plates to be more profitable for a high level smith as a reward for their grind, on top of simply being able to craft higher level gear that's already worth more.
To throw some numbers out, let's say it's a 15% increase in worth, starting at a 5% chance plus 1% per level above the item:
Platebody alch totals:
Iron 336 - 386.4
Steel 1,200 - 1,380
Mithril 3,120 - 3,588
Adamant 9,984 - 11,481.6
Rune 39,000 - 44,850
With the chance starting at 5%, increasing by 1% per level higher than the item, this averages out to a 0.75% average increase to the worth of an item when you're on level, increasing by 0.15% per level. As an example, when you can craft Mithril Plates, Steel Plates would have a 25% chance to craft as Masterwork, an average increase of 3.75% worth.
At 99 Smithing (Metal / Chance / Alch - Average Alch):
Steel / 55% / 1,200 - 1,299 (+99)
Mithril / 35% / 3,120 - 3,283.8 (+163.8)
Adamant / 15% / 9,984 - 10,208.6 (+224.6)
Rune / 5% / 39,000 - 39,292.5 (+292.5)
Examples at 99 Smithing if the cost increase is (25%/50%)
Steel / 1,200 - (1,365/1,530) (+165/330)
Mithril / 3,120 - (3,393/3,666) (+273/546)
Adamant / 9,984 - (10,358.4/10,732.8) (+374/748)
Rune / 39,000 - (39,487.5/39,975) (+487/975)
Personal fav: 25% increase, 1% chance on level, +1.5%/level above
Steel / 76% / 1,200 - 1,382.4 (+182.4)
Mithril / 46% / 3,120 - 3,478.8 (+358.8)
Adamant / 16% / 9,984 - 10,303.4 (+319.4)
Rune / 1% / 39,000 - 39,078 (+78)