I think you need to examine the bolded a little more. You're logic is faulty lol.
How would the loss of Kessel's talent level lead to an improvement in more talent?
Tanking doesn't make sense cause all you're doing is replacing an NHLer with exceptional talent with a player who has potential talent. The result is more than likely an even trade at best, but comes with a higher probability of losing that trade off.
But I get it, can't win with Kessel (he's not the problem people, stop trying to make him the problem. It's not gonna happen. This is why we can't have nice things)
In the short term, losing Kessel (along with the rest of this core) would hurt the team, but you have to look long term, not short term.
Tank is the only thing that makes sense because its clear and obvious that that 1 NHLer needs more exceptional talent in and around him for this team to be ultiamtely successful (ie - a cup winning team) and the reality is that it will be next to impossible to add the kind of players around Kessel that this TEAM needs to become a contender in the next 5 years or so (most likely Kessel's window)
"Tanking" isn't about getting equal value for Kessel in a trade, that isn't going to happen. And its not about drafting that 1 player who will single handedly turn the Leafs into a contender or out score Kessel by 5 goals and 10 points. Its about building a GROUP of players that can be the foundation that a winning team is built on.
We went through 10 years of basically this with Sundin. Great player, #1 center on most other teams during his career, but we were never able to build the kind of nucleus and core around him that could really compete with the Wings or Devils or Avs. We had 1 piece, they had 3-4. "Tanking" is about taking the time and opportunity to get those 3-4 pieces.