These are excellent points that get us closer to considering the question of when big companies are a good idea--especially #1. The ability to operate divisions at a loss and ride out a down economy is certainly an advantage had over the small firm who one might expect to be much harder hit when its core competency is hard pressed by external forces. So, one might be justified in saying a big company is a good idea when market forces bear negatively on participants, allowing the large firm to weather the storm less disastrously than a small firm. Of course, one can counter this proposition by arguing the large firm thus exhibits an unnaturally advantageous existence, not only bypassing but perhaps also eroding, perverting, retarding, and preventing evolution of the market in directions for which it is unprepared and in which it would lose its currently stronger standing. And yes, a similarly framed argument can be made
for the large firm in the context of the evolution of markets--the larger, stronger company is the more fit, as evidenced by its ability to ride out market changes, retooling and repositioning itself for future success when the chaos dies down. However, I think it more likely this is only true as a result of its unfair advantage in having been large enough to not be naturally weakened & removed by the market as smaller firms are--because it is not removed from the market as a result of large concentrations of capital not possessed by smaller firms who are potentially better suited to adapt to changing conditions more rapidly but are forced out due to markets operating in line with extant large-firm bias (even when the market itself could benefit from the loss of the large firms).
#2 is, for me, quite close to the line of thinking offered in the OP, and of course the one I take issue with--it is more a statement of the way the market works now than a solid reason for why a big company is a good idea. I find this is a result of market players operating in such a manner as to give preferential treatment to a large company for reasons that don't actually equate to a larger company possessing this stronger negotiating position a priori. Rather, leveraging an existing preference that is itself an artificial construct (historically built by large firms) atop the market offers little in defense of why the large firm exists or is a good idea. In essence, the large firm enjoys a stronger negotiating position in the market because players in the market prefer to negotiate with a large firm because they believe it is in their best interest to do so because the large firm wields vastly larger capital with which it entices the players to negotiate with it over smaller players. This is circular and, in my view, ought then be discarded in attempts to explicate why this is a good idea.
#3 is a bit harder to pin down. I'm not convinced there is an inherent goodness in brand longevity as far as markets are concerned--or where employees, vendors, clients, or anyone else matters. I also find the material history of humanity and the markets replete with more examples of why leadership longevity is a bad thing than the reverse. There are certainly far more examples of long-term leaders ultimately driving their companies--large or small, it doesn't really matter--into relative oblivion or disarray or irrelevance than long-term leaders consistently innovating ahead of the markets, responding to changing conditions and rapidly correcting course so as to move forward. Leadership longevity often results in market players who have a vested interest in maintaining their position in the market through either coercion, prevention, or weathering out blips. It also can create companies who fail to change with the market because they believe they have it right and the market has it wrong. Perhaps in some cases this can be true ... but the perspective is always funny to me when people discuss "correcting" the market or some similar type of action. Correcting the market has always struck me as code for "get the market back in line with the operational goals of the large firms who have been benefitting the most." When the market moves against them, they seek correction and realignment. When the market moves toward them, they seek protection and cultivation.
Anyway, your points are far more interesting avenues to thoughtfully consider when big companies are a good idea. Not yet to the "Why do large firms exist?" question from the article yet, but at least getting closer to what I thought the author was going to do. And, we're still far from the question the author started the article with in the first place, of course.