"Our weakness is down the middle!!"
Trades 4th line center for a Dman...
Think your logic is a little flawed bud...
if there's any center being traded btw it's Bozak.

Honestly not that far off but we need center depth so the GOAT isn't going anywhere. Something like Kapanen, Rosen and a 2nd will probably get it done. Calgary would probably make that trade for Komorov as well. However don't think the lineup works. I wouldn't expect for Nylander to go Center until next year at the earliest if ever. We have Bozak and Kadri still who should chew up a lot of minutes.

As the line generating the most offensive chances and highest percentage of possession, you don't break up the Leafs top line, especially since they are dying for offence lately. I will predict now that the Leafs will make some sort of move to add center depth in their bottom 6. My preferred choice would be Derek Roy, but there are other options out there, as well. As a side note, though I like the idea of adding Tanev, I am not sure that'd be enough, as far as quality, not quantity, to make that trade happen.

Tanev is lot more deserving than those pieces. Rosen and Rychel aren't NHLers, Gauthier is questionable and a 50th pick is more questionable.
You are correct, the Leafs have little pro depth at centre. And moving Nylander mid season isn't the answer.