I actually think TL does worse. He would be trying to run and getting crushed.
I agree with your assessment. To me, the only way TL is worth the pick you mentioned is if he quietly becomes a top 10 QB and Sam stays around 20th. I don't think the drop off is that big. I would be all in on trading back.
I started the season with a thread about this being Sam's last chance. I. still hold that he needs to show something and do it quickly but I also believe that if Jim Mcmahon and Trent Dilfer can win a super bowl, so can Sam because he is much better than either of them.
Again,
2 good OL
A true #1 WR (and keep the ones they have now)
A decent TE
A good Edge
A lockdown CB
That changes this team dramatically. 3 first round and 2 second round picks would go a long, long way in getting them there