I Darius Quintus, one of the top 200 unluckiest gladiators, have devised a potential successful strategy for my poor century of doomed souls.
Primus: Accept that every single one of us is already dead, because blindfold fighting with shortswords is basically russian roulette with all but one chamber loaded survival-wise. HOWEVER with my tactic we may be victorious! (and by victorious I mean some of our side may yet live.)
Secundus: Draw lots for position beforehand and form into 5 ranks, tightly backed with about a foot of space between each man sideways, and only slightly more front to back. The front two ranks will be side-on to the enemy. We will anchor our line on the left fence. (The majority of us will likely be right-handed, if not all is reversed) The front rank will utilize the standard stabbing techniques of the gladius, at chest/belly level. The front rank will have their left arm gripping the man to their left, with the farthest-left man holding the fence. Should the man on your left die, stab front and sideways until you feel a reserve move up.
Third (I have exeeded my latin): The front rank will deliever the two standard strokes as rapidly as they are capable of for a sustained period of 8 minutes. Given the pace of the murderous back-fences the battle will be over one way or another by then. They need not vary their strokes because the enemy is blindfolded and cannot learn from their fellow's deaths or time the predictive nature of repetitive blows.
Fourth: The 1st and 2nd ranks will use their left hand to hold the man on their left. The second rank will have their right (sword) hand with fist/pommel pressed against the shoulder blade of the man in front. If at any point they cannot feel the man's back (due to his almost-certain death) they will commence the two standard strokes described above until death claims them or battle ends.
Fifth: the third and fourth ranks will keep their blades in their loincloth straps, and be half as many men as the other ranks. The 3rd rank's job will be to keep one arm on the two men in front of them. Should one fall, they will pickly slap the 4th ranker on the appropriate side. The 4th ranker will be walking backwards and have both his arms on the 5th rank "reserve" and pass up his men. He will be able to reach both the two men right in front of him and the ones to either side, which means more reinforcements for a slot in the line than "just" 5 men if things get dicey. Should the 4th ranker no longer feel reserves he is to draw his sword and move as the 3rd rank requires. When the 3rd rank no longer feels a man at his black he is do draw his blade and act the same as a 2nd ranker.
Sixth: the 5th rank will start touching a man in the 4th rank who isn't touching them, to ensure maximum rapidity of passed commands to bring up the reserve.
Seventh: When battle commences the line will move at a quick walk 30 paces, then proceed at half pace. In a perfect world the line would slant backwards towards the center of the pitch to cover the exposed flank, but keeping any sort of complex formation while glindfolded is hard enough that this cannot be relied upon. Therefor the rightmost file will utilize a slashing motion instead of using their right hand to guide. This is the most dangerous position, for if the enemy attacks our flank in numbers there's not much to do but give a word of command (which the men are trained to repeat 3 times when they hear it to ensure it passes to the whole formation).
Eight: Once the word is given the formation will attempt to shift in-place and face the mass to our right. Likewise if the formation goes 100 steps forward (roughly 1/4 into the opposing side of the pitch) and the front-liners give the second word of command to show they have not been in contact for 10 paces, we will face right and advance crosswise. That formation will be the same as described above, but with both end-files slashing to the side.
Ninth: As you can see any motion in the formation brought about by step 6 or 6 will likely shatter the formation as a single block. The emergency fall-back order for gladiators who lose the formation is, if they lose contact with both sides, move directly fowards as best they are able stabbing forwards. If they bump into someone from the side they are to stab if there is any question at all tha the person they bumped into isn't going their same direction. If they are going the same direction the hand-code should be given before stabbing.
Tenth: should a gladiator or group of gladiators which loses contact with the main force contact any fence, they are to put their backs to it and yell my name, stabbing outward continuously. All others on our side are to avoid the noise, so the lost gladiators know anyone coming near is an enemy.
Lastly: All directional contact between gladiators (ie: contact made after initial deployment used to give orders) will be made with a fist that has the first two fingers and the thumb extended, then the actual grab-tug-into-place. Touch is the most noticeable of the sense, and with luck utilizing this method will stop blind gladiators reacting to flailing limbs of the dead and dying rather than actual commands or hesitating if the enemy grabs them.
So there it is. Not a flawless plan by any means. But against an enemy who believes the fight is hopeless and doesn't plan at all it should be enough to ensure they are wiped out before we are. The biggest flaw in this plan I can see is if the enemy copies it exactly. At that point neither force will ever contact the other before we're both crushed to death by the advancing spike-fences. But the Emperor (may he be forever shamed for his poor choice of unique gladiatorial event!) might intervene in that case if both sides look out for blood and just can't find each other!