Anything that takes away the reason to explore this huge world of theirs is basically shooting yourself in the foot. With this gone, why would I bother explore woodlands or generally wild, uninhabited regions
You are appealing to a false correlation here. Having to craft one kind ofpotion just once in NO way necessarily implies that there would be no reasons to explore.
If anything, as I said, if they are clever they could take the chance to make all the reagents to craft one specific kind of potion far more rare and interesting to gather.
Let me elaborate a bit on this point: since there would be no need to offer to the player a constant flow of some kind of reagents, they could make some of them -the ones for the most powerful/interesting/exotic potions- some sort of unique reward tied to an optional subquest or hunt, for instance, instead of having lootable plants every few meters across the entire game world.
As I said in another thread (which wasn't exactly related to this topic, if not in a marginal, incidental way) I wasn't exactly fond of the loot system in TW2, since it mixed an overabundance of "lootable" spots with a craft system that *strongly* encouraged the player to pick up whatever he found on his way, because he was most likely going to need EVERYTHING.
I would honestly prefer to hunt down half a dozen of unique, rare ingredients rather than picking up wood planks, twine and oil at every goddamn corner.