That's pretty logical, but there would still be a lot of players who get upset out of proportion to the actual effect.
If they did a nerf like that, they should add an exception so that level 1-15 characters who currently have the greensteel item can continue to use it with ML 12. Newly crafted items would be ML 16, and a character would be unable to place things in the Altar of Devastation before being 16. Anyone who True Reincarnates would also have his greensteel ML raised to 16 (and the reincarnate NPC would give a specific warning about that effect)