It's not that simple, because of time and STs. First two lines will play 32 or more ES minutes out of maybe 52 total. So you want your best players on those lines. 3rd line maybe plays 12 ES minutes, 4th line 8-10 at most. So your 4th line guys should play the PK, so you don't have to use your top 6 guys and save their legs for ES and PP. Now if you're lucky enough to have 4th line guys who can skate, forecheck, play the PK AND contribute offense, that's a deep team, but odds are they're going to be your 3rd line guys (how many teams go 12 deep?). But you're gonna prioritize energy and defense, because you want them to make the opposing team's offensive guys work (and get better matchups for your offensive guys). The other problem is if you have solid guys on the 4th line, how you gonna pay for them as RFAs? This is why you need to draft well in the middle rounds (and collect extra picks) so you have a steady supply of bottom six guys, sleepers surprise and move up to the top six (who tend to be signed to longer contracts), a few graduate to the 3rd line and either fall off the cliff after a few years or get traded when they become too expensive, the rest cycle on the 4th line and are replaced by young cheaper draft picks every 2-3 years. Look at the Pens, they had two cup runs built around two lines and some young draft picks, Guentzel #77, Rust #80, Kuhnhackl #110, Simon #137, Sheary UDFA, Aston-Reese UDFA. They got Sheahan for Wilson #209 and a 3rd rd pick, Schultz for a 3rd rd pick, Oleksiak for a 4th rd pick The top of the team was build on high picks and big deals (Crosby, Malkin, Letang, Kessel, Hagelin, Brassard, Hornvqvist), the rest of the team through middle round picks, both retained and traded. And one of those picks became a top 6 player (Guentzel).