Mostly due to an unlikeliness of adding something which doesn't come
across as the "right" solution, at least to me.

The trouble I see with this "fix", is that I don't think it really
"solves" the root problem. Secondly, as I've certainly seen with
prep items...limited preps don't work in quite the same way as
limited items. Limited gear is balanced by the rarity and idea that
only a few people will have the "bonus" of the gear, and you kill
them and take it away. Limited preps work differently, because it's
not really a "finite" number of them. Instead of only being able to
use the item occasionally, what I tend to see is that a few very
number of people use the items, regather them as soon as possible
afterwards (in which they have the best information as to when this
item will repop), and repeat - therefore in practice having access
to this "rare" item near indefinitely.

I firmly believe that unless you make this item something like...HLK
or Dragon Lair challenging, the same process of simply repeat killing
to gather what's needed will happen - at least at hero levels,
certainly.

My second reason for disliking this idea is that is continues to
simply expand the gap between new player and veteran, and/or the
"game only begins at hero" perspective. I don't think either
benefits the game. I do like the PC-interaction-required
involvement, though. If *anything* along these lines were
implemented, I think I'd almost prefer a long-timer repeatable
quest where a druid does something appropriately nature-related,
significantly appropriate RP-wise (like Ragers and Veil), and
then give the item to be changed to an NPC to work their magic.
But that's just my idea.

However, this is all being based on the idea that druids *need* to
be able to transmute gear. If we're problem-solving this
effectively, the question needs to be asked - what truly is the
root problem that exists that requires transmute metal to wood to
solve?

It can't be need for non-metal gear - there's plenty of that
around. My only assumption is that it's a perceived lack of top-
tier druid-usable gear. If it's *specific* gear problems like
"There aren't any useful druid-friendly boots around", then I tend
to feel that's more appropriately solvable by adding reasonable
non-metal boots around. In personal experience, belts are always
the weird one. Druid or not, it's belts that I'm always like
"meh, this'll do, since I can't think of anything really more
useful".