? Not sure I follow. VLC is open source, Moonlight (that *other* silverlight) also, mplayer hooks into the browser too, not to mention heavyweights like Java. And that is why IMO Flash (player) must open up or die (feel free to disagree, I'm fine with agreeing about disagreeing ).
But we don't need to go as far - hell, even tweakflashver does exactly what you say, it affects that Flash thingy and the browser and is in Extras. If tweakflashver can be there, so could, you know, real Flash 10.x, too (the fact that tweakflashver is open source is irrelevant - it could have been a binary blob in non-free).