I want the offensive line addressed big time, too.
I like Rackly, but not that much. He may not be Robert "Buster", but that is where the "Buster" came from, along with James Marten. Now, you have to hit on two 2nd and two 3rd round picks. Your risk just went way up. Plus, you just gave away the most talented, gifted, and best offensive linemen in the draft (Tyron Smith).
Cannon has a significant bust potential due to his weight and dedication questions. Dallas should get away from the big, slow footed offensive linemen, and I think Garrett is in the process of taking them in that direction.
You don't give up a blue chip offensive tackle like Tyron Smith (with big time upside), so you can pick an inferior player in the first round and get an extra pick or two among more inferior players.
You are not the only one with your philosophy of trading down at pick 9. You are not alone on wanting to trade down. I'll give you that much, but it still doesn't make trading down the solid, safe, smart move.
You don't get very many opportunities to land a blue chip, cornerstone offensive tackle like Tyron Smith.