Knowing that Acno is in character here, it all depends on how long Dogramag can last as Acnologia would no doubt go after him first as he is a pure Dragon and not a Slayer. Personally, I think DG's are around mid-mid or mid-high diff material for Acnologia, with Dogramag, he likely won't have much trouble with him since he's nerfed as he just woke up. I'd say low diff if Acno is serious, mid diff if he's casual. But. I'm sure Acnologia is serious here.
During the skirmish between Dogramag & Acnologia, Kirin would be the strongest one here and would engage with Jellal or Erza due to them being the strongest after him. I wouldn't be surprised if Jellal and Erza choose a temporary alliance to take on Kirin. This battle would be going on while the two Dragons fight.
Once he's done with Dogramag, I can see Larcade trying to hax Acno, which would promptly get him gutted or obliterated. Acnologia would then go for each Dragon Slayer who should all be one-shot material for him either by serious magical attacks or just straight up blitzing and gutting.
I think Erza and Jellal could stall Kirin long enough for Acnologia to win, I can see Acno targeting Kirin first due to him being the strongest here other than himself and the recently killed DG, he promptly guts him and moves on to Madmole and Larcade who would no doubt go after Acnologia.
With Larcade, Dogramag, Kirin, and Madmole dead that leaves Jellal, Erza, and Sting remaining.
So, my new choices would have to be Acnologia, Jellal, Erza, & Sting, I say Sting because his magic is useful in a situation like this, if he hides, he should last long enough for four of his foes to fall.
