Nice guide, few little things you missed that are quite helpful.
D-throw, D-smash is a great chain throw against some characters as someone mentioned. It is the most effective chain throw against sheik as the effect of DI is minimal. She will just pop up in the air ready to be grabbed again. It also works for captain falcon on higher percentages.
When D-throw - D-air chain throwing, good DI can escape quite easily. When you do your d-throw, make nana move slightly forward before D-airing. This requires a little 1/4 circle rotation of your joystick to move forward then g back to d-air. This will send most characters behind you, so to grab again spin around and press grab.
Edge guarding is an ice climber specialty. A couple of good edgeguards:
1/ Spot dodge to desynch facing the edge when an opponent is off the stage. Make nana charge an f-smash then turn around with popo and wavedash off to edgeguard. This means that if they make the stage they get f smashed and if they go for the edge the miss it. Note nana will smash when popo grabs the edge so timing is important. You must hold a the whole time to keep the smash charging.
2/ Similar to the above, when rolling back onto the stage from the ledge, you can make you nana perform any move. So if you miss an edgeguard, you can smash with Nana.
Another handy desynch with the climbers is up b out of shield. Nana will pop up but they wont perform the up b. Essentially nana will short hop and be able to perform any aerial. This is useful for high percentages as you can defend your popo and short hop attack with nana.
Nanapult. Nanapulting involves desynching your ice climbers (easiest with spot dodge to ice brick) alternating ice bricks, then inputing dash jump and down b while popo is using ice brick. This will make nana run forward, jump and blizzard - nanapult. It's a useful change up move or mindgame, keeps your opponent guessing and can stun them long enough for you to capitalise.
Anyway, just a few thoughts, there are endless possibilities with IC's so just experiment. Use those disjointed hitboxes!!!