1st line yes
2nd line yes
3rd line (maybe) but from reports looks like (Kerfoot-Thorton-Vesey)
4th line (also maybe) but looks like we will see (spezza is the center and simmonds on RW)

def 1st and 2nd yes. 3rd and 4th line is completely up in the air lol but I would be fine with what you suggested.

Lehtonen I think plays on the left side on the bottom pair and then either Dermott or Bogosian get the bottom pairing RHD spot

Lehtonen has played on the right in the KHL, but yea something like lehtonen dermott or dermott lehtonen

Other than Hyman being stapled to Matthews, the top 4 and the starting goalie i dont think we can say any way who is gonna be playing where

I cant fathom that Thornton has the legs for 3C anymore, by the time the playoffs come along will he have enough gas in the tank?
Do you guys want to see Thornton at 3C?

Dermott played RD in junior and AHL.

With Sandin on the way, Muzzin locked in long term, and Rielly being Leafs best dman, if 23 yo Dermott is truly in Leafs long term plans it makes sense for him to switch him to RD now(barring injuries).

Then going forward:

Rielly - Brodie
Muzz - Dermott
Sandin - Liljegren/Holl

With Lehtonen being the wildcard, and a Bogo type hanging around as a 7th if Holl is moved, or Liljegren can't make the leap.

In a shortened season yes, but if it is full 82 then no.

I might even take it one further and say only the top 3 D are set. It's Holl's job to lose, but someone like Lehtonen or Dermott or even Bogo could find a way to squeeze him out of it. Bogo unlikely but you get what I mean

Hyman Matthews Nylander
Kerfoot Tavares Marner
Robertson THorton Mikheyev
Barabanov Spezza Simmonds
x - Vesey

Rielly Brodie
Muzzin Dermott
Lehtonen Bogosian
X - Holl

Tavares line is probably the 1st line (better matchup line) and Engvall probably plays over Vesey

I don't know that Wayne Simmons is 3rd-line caliber player.
For role he is expected to play, I think he could do with 6-8 minutes a night on 4th line.
As someone who watched him all last year, I'd say I would trust Joey Anderson more on 3rd line.