For starters, Werner would have to want to leave for the swap deal being a possibility but latest indications are that he doesn't want to leave especially after only a season, and he said he joined us to win trophies. That's also without mentioning that previous reports suggest Haaland doesn't want to join us.
Also, the talk of this swap deal is "interesting". While Werner may be classified as a striker, he is definitely not an out-and-out #9 or central striker like Haaland is. When Haaland leaves, I suspect Dortmund might go for someone like Andre Silva instead.
Agree on getting any striker anyway but the question, which proven striker can we get? If we can't get Haaland, then who else? Lukaku may be a possibility if Inter's financial situation worsens but otherwise, there's a lack of top strikers out there. If all else fails, think Tuchel might play Havertz as the False 9 instead, something that he has spoken about and done several times.