So I got to thinking, that one Guy was considered to have won 2010 because he made a mockery of HFS, removing the greatest threat to a fort, and living there.
If you define winning as "One guy colonizes HFS and claims to have won the game regardless of the fact that the majority of the forum cries out that it's impossible to win DF". Then yes, he won. Personally I think that what he did was incredibly dwarfy, but it doesn't count as "winning". DF is like the game, all you can do is play until you lose. I mean after all even that fortress where he claimed that he "won" came to an end eventually, right? Whether it is by goblins, HFS, lag, or even boredom, eventually your game ends and you lose. You can't win, all you can do is claim that you can and then don't accept the fact that the majority of the forum disagrees with your statement.
You're being far too literal. Everyone knows there's no winning, and its because everyone knows it that its fun to say that he won the unwinnable game. It's tongue-in-cheek . You could argue that this thread ruins the whole thing by either taking the joke to far or taking it too seriously by attempting to define a future win.
That said, under the premise that colonizing HFS was a win, then i would think the next logical step would be to domesticate HFS as much as dwarvenly possible. HFS batteries spewing fire and poison and webs onto invaders, HFS silk clothing and silk ropes and silk decorations. HFS roasts, crafts, and bone armor. HFS execution pits, HFS fire for water-removal/vaporization. Demon zoos. Although I think AussieGuy has done a bunch of this already.
One sad thing about the HFS parts though is that they have no base material multiplier, and there is no way to add one even after worldgen, so demon-silk cloaks wouldn't be as valuable as pig tail ones.
There appears to be a shortage of people "winning" the game without using exploits. Let's define exploits as checkerboards, danger rooms, drawbridge isolation doors, atom smashing, and quantum stockpiles for starters.
Is anyone Dwarf enough to defeat HFS in traditional army combat, after a long period of conventional military training and forging of many, many masterpiece weapons and armor?
I'm pretty sure someone did. Didn't the guy who originally got a colony into hell do it that way?
It was a long time ago, but if my memory serves me correctly in the thread you refer to, the guy did it by modding various domestic animals to be 100 times larger than demons, e.g. "the stray puppy kicks the Pteradon fiend in the lower body with his back right foot and the severed part sails off in an arc!"
As for defeating HFS in glorious combat, I believe it has been done before with soldiers and regular war animals. 100 + legendaries with the right formation can do it fairly easily, and the biggest determinant of success/failure is how many problematic demon-types you get on worldgen.