My healthy lines would be:
Nylander-Matthews-Kase --> Gives Matthews 2 guys with great IQ, who can get passes to him, shoot it, and gain the zone. Also Kase would be good in a more offence oriented role and can still act as a digger.
Bunting-Tavares-Marner --> Bunting works well with Tavares and gives Marner a second net front option
Kerfoot-Kampf-Mikheyev --> this should be a really good two way line, and you also have Engvall who can tag in. The goal here is Tampa L3 style, and these guys should be competent, and if it fails you can always drop Kase down and move someone up.
Ritchie-Spezza-Simmonds --> Ritchie is way more suited for this line, and Simmonds/Spezza have both been great so far.
Engvall --> good ace to have
Rielly-Dermott --> arguably our 2 best defenders so far this year, this also gives us time to see what we have in each of our young dmen. This pair would be really effective in my opinion, and Dermott is more physical than Brodie, which we could use.
Sandin-Brodie --> We test run this completely to see if it could be our top pair next year, simple as that. Get Brodie to cover Sandins defensive deficiencies and we're in great shape here.
Muzzin-Liljegren --> Muzzin can mentor Liljegren, and this would be a nice heavy pair, would look great out their with our L3. I would also run all the pairs 16-18 minutes a night before special teams.
Holl --> he's sucked, and his only place is with Muzzin or D3, and frankly Lilly needs game time. Holl can rotate in
Campbell --> straightforward
Mrazek --> see above