Hooray for Balloon and Blaze Wall.
4b: Past and Future
Team SnowFire vs. Lufia, Lucia (S2) Child Rydia and Valvalis (FF2/4 or FF4a)
Right, warmup fight. Lucia & Child Rydia are really the only threats here. Not sure if people see Lyn as able to counter Lucia out? I know at least some of her attacks hit a line in S2 so would be GT and thus not eligible for counters. Val spins, Lucia starts attacking Lyn. Jess unloads with Kaboom, Lyn hits Lucia, Garnet picks an appropriate summon and smashes. The combined weight of that MT should mean that Lufia & Rydia are dead, and Lyn's attack means Lucia is dead too. Purim or Rena heals up Lyn, and it's Valvalis vs. the world. Worst comes to worst is that Lyn somehow dies, but if you have more Dungeon Team durability respect, then Purim tosses in an MT Blaze Wall to finish the job (it's good damage!) and Rena either MT heals/Revives Lyn as necessary.
Once it's Valvalis alone, Purim has Remedy for her Stone, and the team has plenty of healing otherwise. Jess tosses Kafrizzles at her until she's dead.
Team SnowFire vs. Rikku (DL Legal), Aeonless Yuna and S5 Georg
ItemGurl16: chek out my sweet balloon!
Gullwinger: wooo! screw fighting let's hold a concert instead! WITH BALLOONS!
DeathblowG: .... I must now kill you all.
ItemGurl16: ur jus jelous u dont have a balloon
Georg can halve status hit rates in general at the cost of tanking his defense, but Georg ain't winning this alone. Lyn takes one for the team, Purim takes her turn and Balloons the team. Revive & Heal Lyn afterward, take another shot at paralyzing Georg if it failed before. Alternatively, Garnet's summons probably nuke the hell out of his awful Magic Defense anyway. (Strangely enough, they'd be less effective on later floors due to the low FF9 damage cap, but damage average is probably in the 2000-2500ish range, so not an issue on floor 4.)
Team SnowFire vs. Fort Zeakden Algus, Balk, Undead Dark Knight Argath and Undead Balk
I don't let FFT bosses switch equipment, which means that Purim getting a turn = oh god we are all on fire. If you do let them juggle equipment, they are almost exclusively ST, meaning the old "buff Lyn with Defender & Protect" strategy works like a charm. Argath can only break Lyn's sword at worst, Remedy handles Arm Aim.
*Full Heal
Team SnowFire vs. Gun Mage Yuna, Thief Rikku and S2 Georg
More MT paralysis! Rikku tries to stop Lyn, but even if it hits, Georg still has to kill Lyn. If you let Stop turn off Firefly, then Georg attacks Purim, but he needs a crit, and I'm not sure that even a crit is a OHKO here? Depends on the S2 damage average used. Anyway asking for both Stop to hit and a crit to hit are pretty low odds, and this only even applies under the harsh application of Firefly and high S2 damage respect.
Team SnowFire vs. Lufia 2 Erim, Lucia (S3), Barbariccia (FF4 DS) and Rydia
Init order (with 1.00= average speed), note that Lucia needs to pick a form:
Lyn: 1.29 (can voluntarily slow herself down by holding a Steel Sword if she wants to go after Jess)
Jessica: 1.25
Barbariccia: (?) ("Above average" speed, theoretically fast but not really in practice according to stat topic)
Speed-twinked physicalling Lucia (with lower defense and no status resistance): ~1.22
Garnet: 1.09
Purim: 1.00 (ARPG. If you feel nice you can give Purim a speed boost on turn 1 due to not needing to close with the enemy with her spells.)
Rena: .90? (SO2 Mage. I call Mages a bit slow - don't need to run up to the enemy, but casting times can be a bit slow. On the other hand KMs can take time too, just that they tie up one enemy. ARPG headache.)
Erim: .71
Rydia: .68 (varies by form, going off FF4a's stat topic, generally slow)
Explosion-casting Mage Lucia: ~.66
Ahem. The biggest threat, if she lives, is Rydia. Luckily Lyn *murders* her on a double. Jessica... has options, notably Accelerate for the long game or Kaboom for the short one. Let's say Kaboom for now. Barbariccia needs to decide whether to Spin or not - she's slow enough in FF4DS that she's basically delaying her action for a round, since she doesn't 3:2 average anymore. Waiting is *bad* for reasons that will soon become clear, so she hits Lyn and eats a counter. Let's assume whip-Lucia for now, and let's also assume she manages to hit Lyn (she's got good Accuracy and this version of Firefly has an evade penalty, so sure). So Lyn is now dead
and the quest is over 
.
Garnet revives Lyn. Purim Blaze Walls the team. Fun Fact: Barbariccia can be paralyzed (...). WTF. Rena heals the team. Erim can unleash Dark Fry or go for cruddy 15% MT ID. Dark Fry is only .44 MT physical damage, so it's not really that bad.
Next round. Jess Kabooms again. Lucia is magically tanky but she's now eaten 2 Kabooms and a Blaze Wall. And is also paralyzed? Okay, assuming she threw away a Feather Earring for a Yellow Scarf, if she's still alive, Lyn was revived and healed. So attacking against Lyn likely gets her killed on the counter, but charging a spell gets her murdered by Garnet's MT summon. So she gets some damage in on Lyn. Garnet casts a Summon, and now Lucia is down for the count for sure. This leaves it as a paralyzed Barb & Erim vs. the world. It's over.
Now that I think about it, the only real threat in this fight is Erim's 15% ID getting lucky. On second thought, a safer way to do this fight is have Jessica open with Magic Barrier. Magic Barrier is basically a flat -20% to status hit rates - 100% chances become 80%, 65% chances 45%, etc. (It's somewhat inconsistent- against some attacks, it's -30%, and others it's -10%. 20% seems the most common.) So this should totally null Erim's ID, and the extra offense from a Kaboom isn't really necessary as S3 Lucia isn't a big enough threat.
If Lucia had gone the mage route, then Lyn would be alive, and Garnet wouldn't have had to revive her. This means she's eating Garnet's best summon and whatever cruddy damage Rena can offer - or, alternatively, Rena casts Anti, which will make Explosion kinda fail.
