Well, that's part of an answer to my question (how long can the Leafs suck/ draft in the franchise-level elite spot?). Nylander and Marner joining the team shouldn't hurt that too much. But is this team as stripped down as the Chicago teams that drafted Kane and Toews? The one that drafted Crosby? -- There are still some serviceable, albeit overpaid and so (apparently) unmoveable, NHLers on this roster...
All bad teams have serviceable NHL players. Look at the Oilers the last couple of years. In addition to a ton of young offensive talent they've had guys like Andrew Ference, Boyd Gordon, Benoit Pouliot, Jeff Petry, David Perron...all guys who are legit players who have either played roles for good teams or that good teams thought enough of to acquire.
I don't think the rebuild will be particularly fast because they've already got some good players. I'm not optimistic about that. But I'm not optimistic that they'll be drafting in the lottery range as often/for as long as we'd like if (a) they haven't moved out any talent besides Kessel, (b) have improved their coaching staff, (c) are getting better at identifying useful contributors in the FA market, and (d) have some high-end talent joining the team in relatively near future... Does it only seem possible to me the closest they get to the Kanes, Toews, Crosbys of the world -- the franchise cornerstone types -- could be Nylander, Marner, Rielly, and one of Puljujarvi, Chychrun, or Tkachuk?
I'm pretty confident that 1) the people running the Maple Leafs are at least as smart as I am and as such can figure out what I've figured out and 2) they can figure out a way to be at the bottom of the league.
As to the specific concerns:
A) Just because they've only moved Kessel this summer doesn't mean that's all they'll be able to do. We haven't heard much about them hard shopping Kadri or JVR or Gardiner but I'm guessing that if they did, they'd be able to find takers. Others, like Polak will certainly be dealt this year and quite a few of the "untradeable" players you mention might be more attractive to teams with less time on their contracts. The tear down, like the rebuild, isn't going to happen overnight.
B) I think you're both drastically overrating the impact coaching will have on a talent shy team's record and underestimating Babcock's ability to engineer the results the front office actually want.
C) The results of which have yet to be seen. All we know from the off-season this management team has had is that they've got no real interest in anyone who will credibly make a major impact in a short term sense and, realistically, very few guys who'll even be on the team next year.
Regardless, if they've gotten really good at identifying what UFA's will contribute heavily to a better record in the short term then, presumably, if they want bottom of the league finishes they can choose not to sign those players.
D) As mentioned previously, being realistic about the "high-end" talent the Leafs have in the system means expecting major contributions from them 2 or 3 years down the road which was the number of high lottery picks that corsi fenwick thought they'd have.