I know I took ages to actually respond to this but I had other stuff to do including prep for ps4
I think this matchup should be played very carefully in phases which are mostly based on your %, popo's %, nana's %, your location relative to the platforms on whichever stage you're on (ban FD), distance from the climbers, the position of your c4, their state (synched or desynched, and with which moves). It is a very complicated matchup to get a grasp on, but I do believe snake gains a slight advantage from human error.
Generally, when I play this matchup it ends up as a game of cat and mouse. Snake is the mouse, and the ice climbers are the cat that wants to eat the snake. The Snake defends himself by blowing himself (and them) by holding live grenades and daring them to start eating him.
Real talk. At low % at mid range (about 2 bowser lengths in front of snake) you either want to close the gap and grab them or retreat onto a platform or further back on the stage, depending on what they are doing. If they are shooting ice blocks or otherwise desynched, you should retreat onto a platform immediately because it is in this state that they have the most options to screw you over with. If they are synched, it is mostly safe to fthrow/bthrow one and then grab the other to throw in the other direction. However, grabbing them is easily countered by ice blocks and blizzard.
FROM NEUTRAL:
At long range, you want to stop their desync tricks by throwing grenades at them, since all of their tricks to get and stay desynched put out hitboxes, you will eventually blow them up. If this separates them, it is generally safe to go in if you are above 30% and beat up nana like a rag doll if you can get over to them fast enough, otherwise you just want to stay put rather than press your advantage because if sopo grabs you at those low %s without cover you will die when nana gets back to him. Try to keep a c4 around the middle of the stage between the two of you as well; it works as deterrent to keep them from rushing in and trying to grab you.
Pivot grab is a very powerful tool for aggressive ice climbers in this matchup; you will usually beat bad ics players by tossing them in opposite directions and fsmashing nana.
If you absolutely have to approach, do it only with grenade cover. Dacusing to pick up a grenade while moving in and then spotdodging the explosion is viable, however if they grab you anyway they can hobble you so that you're invincible on getup when the grenade explodes, effectively leaving you stuck in the chaingrab. However, despite it being possible, I have only heard of or seen lux do this before.
ON A PLATFORM/ABOVE THEM:
Generally, you are not at risk of getting grabbed while in this position. However, you are at risk of being hit by their (imo) next most threatening tool, which is their powerful up air, killing back air, and their low knockback neutral air. All of these moves are a pain to deal with and imo snake is at a severe disadvantage when forced onto a platform if the ice climber player knows what they are doing. It is even more dangerous in many situations than being near them on the ground in my opinion because synchronized up airs do absurd amounts of damage and back airs offstage can kill at fairly low (for snake) %s. if you airdodge an up air, back air can hit you as well, so it may sometimes be better to take a hit from their up air and di away than airdodging. You should also be sure to take the strong up air hitbox as it is more likely to detonate your grenades.
With proper spacing, their aerials will not hit newly pulled grenades. When you are standing on a platform, their neutral air (if it hits) will both hit UNDER your grenades and send you tumbling off your happy place right into an ice climbers grab. There really is not much you can do about this other than avoiding the situations in which it can occur.
When recovering, try to always land on a platform with grenade cover because of their deadly grabs. This should be a given, but do not get predictable with your landings or you WILL die, unfortunately.
BODYING NANA/WHEN THEY ARE ABOVE YOU/RECOVERING
The fun part of this matchup comes when Nana is separated from Popo by enough distance to make nana stop taking player input. You can pretty much do whatever the hell you want to her, as long as you remember that she ALWAYS DIs towards popo and solo ice blocks once to gain height while offstage. Forward air and fsmash are good options for this situation if you can keep sopo away from you long enough for them to work their magic, but I find that a combination of up airs, back airs, ftilts, throws, and up tilts are the best way to deal with this situation. Just use your best judgment to determine the right option for the situation, and try as hard as you can to not let them return to the stage in one piece. You should not worry about staling your kill moves in this situation because sopo is easy to kill and has no effective recovery, meaning that once nana is dead you probably have the stock. Just look out for the low % solo chaingrab after nana is dead because with a fully staled dthrow they can do an insane amount of damage with one grab.
When they are above you recovering, you want to capitalize on this situation as much as possible as it is the only situation in this matchup where they are really not a threat to Snake. Upsmashes, shieldgrabs, uptilts etc are very good here because their aerial mobility is very poor. Edgeguarding them is a little trickier than trapping their landing because there are 2 of them, but if you are paying attention to what they are doing to get off the ledge it is not that different from any other character. You can also neutral air of jab a single climber out of squall hammer and it will send them into free fall while the second climber continues the move solo; squall hammer with one climber is unsafe even on hit and you can uptilt them out of the endlag.
I know this is not very organized, but I do not have any experience doing write-ups and am just throwing around my thoughts on it as a snake who plays it more than any other high or top tier matchup.
Phew.
