Reliablitly in general comes to mind as does fail safe extraction as
@bruce moulds pointed out. I guess as with any ego based, minimalist or extreme hunting pursuit, it will work until it doesn't.
I am not suggesting that Levers should be used, I just see how they can be used. To which I would add:
1) The model 700 fails on extraction (and on controlled round feed). But the solution was to mill in a stronger extractor. Is that an option for these levers? In the case of the Marlin, WWG just made a drop in extractor made out of quality metal. Done.
2) For sticky round extraction, options include: a) Using actions that are capable of properly handling full power loads with enough volume in the case that we do not get excessive pressure; b) An action job; c) Properly designed levers. There have been a variety of big loop levers that have gained popularity recently, and that make extraction and speed more difficult. Since a lot of these levers are actual, or fantasy, NA DG guns, a rethink of what shape the levers should be on a DG gun might be useful.
3) Lupo got a lot of people excited over Marlin 45-70s. It was cool to think one already owned an "elephant gun" and only 15 years ago, those were selling for 400 or so dollars. But several things have happened. Marlins are great, but they also had a lot of problems. Basically, they were too small to do what needed doing, in terms of velocity, bullet weight, and SD. And the guns were underbuilt. Since then, we are 2 reorgs in, and the 1886 scene is more robust than the Marlin scene, with half a dozed makers (probably some overlap in those numbers). Right now we are at 0 for Marlin production. If we can get the ingenuity directed towards the 1886s, in time we may have something. Turnbull has done a lot, but he meets the needs of the bespoke community, and does not affect what people who live in the woods buy or carry.
4) Last summer I zigged when I should have zagged, and did not pick up a Winchester 1895 30-06 for my 9.3x62 project. That gun should be more than competent enough to function with that cartridge, though it is at the low end of the spectrum for a Big 5 DG gun. Maybe between WWI, Roosevelt, And it being 126 years old, it would not be too insulting to PHs who rightly favour the bolt.