So I went over this thread just now and I'd like to summarize what has been established so far and to add some of my own opinions to this.
16 different movesets have been proposed to be the best of all the 81 possible sets: 2231 2211 2232 2212 1231 1211 1232 1212 2331 2311 2332 2312 1331 1311 1332 1312. The moves (PAL names) Blade Flurry, Airborne Assault, Power Thrust and Super Slash Dash do not appear in any of these sets. What should be noted is that this proposal came on march 8, 2015.
Since then there have been several patches that have made a significant impact on most of the special moves.
Most notably is that Blade Flurry is a lot more consistent now, the angle of Airborne Assault has changed somewhat, the range on Super Slash Dash has been buffed significantly, Hero's Spin is slightly more powerful, Shuriken of Light is more powerful and the endlag on Chakram has been decreased by a whopping 10 frames which resulted in Mii swordfighter gaining an unguaranteed but hard to deal with 0-death combo once it starts, as well as a guaranteed 20-40% combo.
Experience and more experimentation has also led to the idea that in the height to weight ratio the most optimal ones for Mii swordfighter are 0:0, 25:0, 50:0 and heights in between.
This has caused a lot more sets to be proposed, but what remains the same is that some moves are still considered to be better than others. I think the best approach to determining the best movesets is with a Sherlock Holmes-esque approach: eliminate everything that doesn't work (well) and you will end up with what does.
By eliminating certain specials you can significantly decrease the possible good sets, especially if you knock one off of each of the directional inputs. I'll explain with some math. The total amount of possible sets is 3*3*3*3=81. If we were to eliminate one special of each directional input, we would remain with 2*2*2*2=16 sets. That's a huge decrease. Actually, knocking just one off gives 3*3*3*2=54. This difference gets smaller once more and more moves get eliminated, but I think you can clearly see this is an effective method. I hope we will use this until we remain 6 sets max.
Therefore, I'd like to list some moves of which I personally think aren't very good specials and I'd like it if everyone would cast a vote upon them as follows: bad (-2 points), situational (-1 point), meh (0 points), okay, I guess (+1 point) and no, it's good! (+2 points). I will update the list with some more suggestions if need be and then I hope everyone will vote and discuss upon all listed moves three weeks long, considering March is the deadline. At the end of that three week period, the points will be counted and the one with the least points is officially eliminated from all considered movesets. People who aren't very familiar with Mii swordfighter aren't allowed to vote, as they don't know what they're talking about, unless they are smash pros like Zero or Esam, because players that good can understand a character well enough regardless. And by not allowed to vote, I mean please don't, because this is serious.
An slightly alternative system is to vote on one move at a time and if the total points are 0 or below, it will be eliminated.
If someone knows how to make those official vote things on the site forums, please consider it for this vote. If we work in a system like this, results are bound to come.
The list:
Airborne Assault remains an unpopular choice because of it's an unforgiving, high risk, high reward move. A big risk most players like to avoid. Thus, it it is considered to be not that great of a move, especially compared to the alternatives of Chakram and Surging Slash. The one thing this move can do like no other is covering a lot of horizontal distance. It therefore as recovery utilities, though the still evident great amount of landing lag tends to make people question the viability of such a use, especially since snapping onto the ledge is no easy task with this move even when taking the opponent out of perspective.
Power Thrust is also a move that faces some controversy, as it is extremely punishable on shield and perhaps not the strongest punishes Swordfighter possesses, even at a distance. In the air, this move will make Swordfighter go diagonally down-right at an approximately 30 degree angle in relation to the stage. The distance covered using it this way is quite a lot and if swordfighter hits the stage during the move, his sword will be stuck in the stage and he will pull it out in an unskippable animation, resulting in lag of about a second. Hitting the ground with it does have a second hitbox much like Dair has, but more powerful. If an opponent is unfamiliar with the move and shields it only once, they will get hit anyway. They can, however, just keep shielding and punish accordingly.
One would therefore reason that this move is best used off-stage, although even here complications arise, such as compromising swordfighters own recovery.
Lastly, another use for this is to escape pressure from below in case an opponent is juggling you.
The alternatives are counter and Reversal Slash, which each are good dependant on the matchup.
Blade Flurry isn't necessarily a bad move, but it can be considered redundant. This is because the damage, knockback and endlag are quite similar to that of F-smash. The damage is slightly higher while F-smash actually has more range. There are four things this move has that F-smash doesn't. These are better shield damage, more pushback on shield, shorter startup lag and a longer duration. The latter is a double edged sword, in the sense that it's easier to punish with, but also easier to be punished for.
It's mostly that shorter startup lag in comparison to F-smash which makes this move chosen, as well as the fact that you can charge it in the air.
The alternatives are SoL and Tornado Strike, two excellent projectiles which can be key in Swordfighter's game.
Back in the stone is flat out a bad recovery move, especially compared to the alternatives. Then why use it? It's because it is the only move in swordfighters arsenal that has a hard spike and it deals quite good damage, making it a decent OoS option, though there are better OoS options.
the alternatives are Super Slash Dash and Hero's Spin. SSD has excellent recovery utilities but little to no offensive uses. Hero's Spin is a strong OoS option and can KO at high percents, but has bad horizontal recovery when there is no horizontal momentum the moment it is used.
Surging Slash is found to be useful as it is similar to Ike's side B, but with the benefit of passing shields. It offers decent horizontal recovery and can be used as punish, though in the latter use it can be questioned if Swordfighter possesses stronger punish options than that in most situations. Unlike Power Thrust, this move goes horizontal no matter what, though it does not ignore previous vertical momentum. The lag on it isn't the best and is more compared to dash attack, but isn't as bad as on Airborne Assault.
That completes the list for now, I think. More detailed descriptions can be found in the Mii Swordfighter Guide. Did you find an error in a fact? Please do let me know.
Let's get to voting!