"It has occurred to me that Flash on Linux is the one major entry barrier controlling acceptance of Linux as a viable desktop operating system."
It has occurred to me that for the past decade, every Linux user has thought his most recent personal itch was the one major entry barrier to Linux desktop domination, and they have all been completely wrong.
The major entry barrier to Linux desktop domination is that even if you're a hardcore Mac or Linux or BSD guy, Windows simply doesn't suck that much. In general, any reasonably competent computer user can sit down at a Windows machine and get his work done. He may have to go out foraging for the right tools, but they're out there, and they're readily accessible.
Meanwhile, there is a vast community of computer users who are NOT reasonably competent, and while they may not be particularly good at getting their work done on Windows, they are EVEN WORSE at getting it done on anything else.
When retarded people can use Linux, you might have a shot at desktop domination. Until then, don't bother.
Adding features does not necessarily increase functionality -- it just makes the manuals thicker.