As a one-time thing, or rarity, buying a pipe and then revising it in a fairly major way by refitting it with a different style stem at considerable expense, might make sense, if the briar is one you love and the remodeling will make it perfect in your mind. Usually most find it satisfying to shop until you find pipes that are brought together by the artisan or manufacturer in a way that feels excellent to you. That's the satisfying way to buy a pipe. But I loved fitting a few cobs with Forever stems, and find the "new" pipes extremely satisfying, so I get the idea. It not the way I usually buy pipes.