You explained and elaborated very well on why I've always thought the PC was doomed to win. By the early 1990s, IBM compatible hardware was not under the control of a single company anymore. It was an ecosystem which could survive the death of any one company, and where innovation can be driven forward by any of its participating companies. Suddenly the Amiga's custom chips don't seem so sexy anymore; before 1995, PCs were rocking high-res video cards with their own blitters and sound hardware capable of CD-quality sound, in multiple channels sometimes (see Gravis UltraSound). The main proprietary link was now in software, to wit: Windows, but when Linux came along Windows was no longer the sole linchpin.

So I think you're right. There's no universe in which the Amiga was a serious contender. Every company is at risk of management blunders or changing market tides, and the scene is littered with the corpses of proprietarily integrated platforms that fell with their parent companies: not just the Amiga but Atari ST, SGI, Sun, DEC, Lisp machines, etc. The PC ecosystem outlasted them all and just kept going on, delivering the advantages those systems had in a cheaper, more accessible package.

The sole exception was Apple. I think Apple won in the long run by subsidizing Mac development with iPod/iPhone/iPad sales, and what this means is yet another market turn away from general purpose computing and toward devices that only run approved curated "apps" and are discarded rather than upgraded. Maybe Commodore could have anticipated this back in the day, but it would have been against the Amiga spirit I think.

I still love my Amiga 500. What it can do was amazing in the late 1980s, and I'm content to appreciate that for what it is.