How would you beat this AR team?

Plop down giga chicken and watch her kill everything except blyn in one round.

Maybe have Cecilia sac to take out Rein, and go from there. Alternatively, have LEphraim sac to take out Aversa, since fake traps don't end turns, and go from there...Can't think of any other solution that doesn't involve at least one sac.

Go up the right side and have Kliff facetank

I wouldn't. Just being honest here.

The only super-tank I have ready to go is Surtr and I'm not convinced he'll hold up under that much pressure, so I have an alternate plan.

I have two teams with dancer, L.Ephraim, L.Hector (using armoured boots and Ostia's Pulse), and SM Eirika. One team has 5th member B.Celica; the other has a 2nd dancer.

Step 1: have someone break the flowerbed and lamp post. L.Ephraim goes where the lamp post was; dance him from the left, smite him onto the gravity trap with L.Hector, and run away to where the flowerbed was. The gravity trap cannot affect L.Ephraim because he has too much HP. (I happen to have +HP, so even if you upgraded it and he wasn't a bonus unit it wouldn't hit him. But it super won't hit him because he's a bonus unit right now.) This can all be done in one turn.
Step 2: I need to get the armour school out of the way. There's several ways I could do it. One is to hit it with SM Eirika from the square without a trap, dance, and have her use draw back on the dancer. Using my team with two dancers, this should be doable on turn 2.
Step 3: setup. SM Eirika goes on the square left of where the lamp post starts. L.Ephraim is in the starting square diagonal to her, which starts out blocked by the lamp post. L.Hector will go behind him to smite him forward again - I always keep this column free of offensive structures because I need that square on a lot of maps and I recommend everyone else do the same. I think I should be ready to go by the end of turn 3, or at the latest turn 4.
Step 4: SM Eirika takes out Xander. I doubt you can OHKO me when I have an HP seal and no bane in HP or def. I don't need to put any unit adjacent to her so Aversa can't panic and debuff her. Smite L.Ephraim forward; he will galeforce Reinhardt and then take out Aversa. By this point I've hit your real gravity trap, so I'll do it from the position of the fake gravity trap. Now, if I use the YT Olivia team, I use WoM to move in front of Eirika, dance Ephraim, and go on the square without a trap to break your catapult. My other dancer will WoM in to dance Eirika from where she broke the armour school, and she takes out B.Lyn. By the latest, I have ended turn 5.
Step 5: your Olivia would probably die if she attacks Ephraim, so she'll hit my Olivia, and we'll have a draw. Ephraim will hit one aether structure, and the rest of the team can either run away or maybe we can dance Eirika over to hit the other aether structure, but the tactics room might get annoying. I still have one turn left.

The rest should be easy.

If your Xander isn't tanky enough, I might just smite and galeforce him with B.Celica. Not assuming that though because the guy has a lot of natural def.

The other possibility is using both galeforcers. Step 1 is the same, but afterwards:
Step 2: clear the bolt trap if your Reinhardt is super-tanky or if your Aversa hits really hard on her own so that B.Celica dies in one hit if she's short 10HP. Probably I can skip this step because B.Celica can double Reinhardt and get a galeforce without double lion.
Step 3: setup. L.Ephraim will be where the flower bed is. He has too much HP for Aversa to panic and debuff him. I probably put Eirika next to him, in front of your fortress, just to make sure Aversa can't double him. B.Celica will stand immediately in front of where your offense tactics room is. Hector will be where your catapult is, and my dancer will go in front of B.Celica just outside the red zone.
Step 4: B.Celica will draw back on L.Ephraim to the right, and he galeforces Xander. Dance B.Celica from the left and smite her from behind. She will only move one space because Ephraim is in the way, but it won't matter. She'll run in and galeforce Reinhardt. Ephraim takes out YT Olivia, and B.Celica will take out B.Lyn. That will be it for my turn. Aversa will hit B.Celica because she gets more damage without triangle disadvantage.
Step 5: from here there's a number of ways I can do it. If I haven't already cleared your fake bolt trap (or maybe even if I have), I might step on it to try to break the catapult. Then I'll use WoM to move between Celica and Ephraim, dance Ephraim, and use Celica to trap Aversa against your tactics room. Ephraim can then break your aether pots at his leisure, while Celica can end Aversa anytime.