The problem there is that nodes don’t always give you 4 of an item. Sometimes you get increased yield, sometimes you get an extra gather attempt, and whether you can use skills (and which skills you use) also affect things, not to mention the possibility of not having a 100% success chance to harvest a given item. Yes, Miqo could – if it was implemented – stop gathering once you picked up a certain count of something, though you could never guarantee you wouldn’t go over, but that’d be more to support when the game updates.
In the meantime, use Teamcraft to get notified when you hit your threshold, and either approximate your gather node count or just do what I do and set node count to 1000 and store or sell the extra.