Lol you know my thoughts on this. I think as long as babs is coach, you aren't going to get your wish though.

Probably true.
When I look at the best lines in hockey, complete players playing with other complete players, different skillsets mind you, i look at the Leafs top six and believe they could have 2 of the top 5 lines in the game if they wanted.

Jason Spezza is pretty slow, so I don't see him doing anything beyond taking face-offs and handling under 10 minutes a game as a fourth liner. Trevor Moore is probably going to be given a chance to replace Hyman, while he is making his way back from his surgery. As you have it now, nothing I can see replaces Hyman. Neither Kapanen or Johnsson does as much of the gritty leg work that Hyman does.

Hyman will never be a goal scorer but he is the perfect 'grit' guy for a line with JT and MM. He gets them the puck and does all the dirty crap in the corners all while being an actually good player. He is like a half priced (but 90% value) Jason Zucker.

Matthews and Nylander with just about anyone will be one of the top lines in the game, same with Marner and Tavares. What you need to do is find a 3rd guy that maximizes there skills. If you look at Boston's perfection line, all 3 are willing to crash the net. So having all their skill together works so well. Matthews and Nylander do their thing better than anyone else at 5v5, they just need someone who fits with that and enhances it. JT and Marner do their thing and Hyman did a lot to give them the time and space they needed to do that. Him fighting in the crease often gave Marner and Tavares clean looks and goals that goalies could have stopped. Those plays don't show up on the scoreboard but they are vital to a lot of goals being scored. I don't think Johnsson is that sort of guy, he's more of a rush player that gets great looks in the slot and can dart through lanes and stuff, a great player but he should have the puck on his stick more so putting him with Kap and Kerfoot, I think maximizes his skills better than having him be the 3rd wheel on one of the top two lines.

He is the perfect grit guy and I love those charts. On the left it shows that he gets lots of chances but doesn't finish and on the right, it shows him as a warm body in front of the net.

He may in fact be the best fit for those two, a work your ass off bottom six guy. But I look at how good Tavares is and his history of elevating his wingers production, and think there has to be better options to get even more out of him.
80 points is nothing new for him, 4th time, and his jump in goals can be attributed to Marner's playmaking ability. Does a 60-70 point winger boost them both into the 100-110 point range much like much like the boost Pastrnak, Lindholm, or Rantanen provided their respective linemates?

I don't put any stock into the Power play side of the chart (the one on the right) as he only had 17 minutes there all season but Hyman's underlying numbers have looked good for awhile now. He is a good player to pair with guys like JT and Mitch. Would I pay him 5.5 for 5 years? Not likely (especially with Moore coming up) but at his aav (hell I'd go to 3.5) he is a perfect Leaf.
Lindholm is an interesting story. I won't copy-paste an Athletic article but he is primed for regression.
https://theathletic.com/1094362/2019/07/25/tulloch-the-nhls-top-10-regression-candidates-for-2019-20/

Johnsson is a wild card for me. He put up a lot of points away from Matthews last year and could theoretically drive his own line. However, he could also be a great complement to Matthews and Nylander and give them that extra element that Boston's line has. He could also slide into Hyman's spot to start the year.

We know what Hyman brings to the table, the question I have is whether there is someone else on the team that can bring more and can Babcock find it if he is forced to.

Can he put up similar numbers in a depth role against weaker competition if, for instance, Moore emerges or someone else?

While Lindholm may regress, that line was special last year. Gaudreau was up 15 points and like 12 goals from the year before, 18 points for what's his name the centre, and it wasn't a boost on the PP either. It was all even strength.

Currently no, there is no one that can do what Hyman does as well as he does it. I think Mikheyev could do some of that but he'll be a better scorer. If he can learn to do what Hyman does then great, Matthews line will be sick. If not it'll still be sick with Johnsson there.

Numbers? Not likely. Level of play? Almost certainly.
See shooting % regression for the Calgary line. 4 real consider getting the free trial at least to gain access to things like that. It is well worth it. (or buy with the 50-60% off vouchers. They never expire so just google around for them)

I'd say the only way it boosts Marner and Tavares higher is if whoever replaces Hyman can do what Hyman does and also score. Currently there isn't anyone in the Leafs system who fits that bill. Comparing them to Boston's top line isn't really a good comparison. JT can be compared to Bergeron I suppose but Marner isn't the same player as Marchand and Pastrnak is a bigger guy who can crash the net as well. They always have someone near the net which is why they are so dangerous. Marner isn't really a net guy, so you need to find him another net guy and Hyman did just score 21 goals. Its not like he can't score.