This has a lot of moving parts thanks to the nature of the ambush and the fact that while we know it's an ambush, the particulars of it are hard to plan against since we lack the information for it.
We know their goals however, and the means they have on hand to achieve it. To summarize, our foes want Justice Unlimited dead, and they do that by killing Lady Leizi in an ambush.
- Scarlet Maturity - THE Brick. Regenerates so fast, wounds don't matter to him, and he's physically the strongest person on the planet.
- Été - Ally Buffer and leader of the 4 Seasons. Able to create fiery weapons.
- Printemps - Plant manipulation. Able to grow plants that shoot people and grow in size.
- Hiver - Forcefield creation, and our mole on the inside. Able to create barriers that keep things inside or outside, while also manipulating the direction of gravity in the area caught inside said barrier.
Note that considering Earthen Owl had improved powers, there's a chance that all of the above have new tricks. We'll need to watch out for that, but it does mean that Hiver might also have new abilities.
[X] Plan:
Quoth the Raven
-[X] Lady Leizi (Shield Generator)
--[X] She will represent Justice Unlimited during the meeting with 4 Seasons and fish for information until Été either turns hostile, or Scarlet Maturity is spotted on the move, at which point she will attempt to knock the two out with Handyman, Hiver, and Menagerie Witch's horde before making a run for the Apiary.
-[X] Black Swan (Shield Generator)
--[X] On overwatch on a vantage point overlooking the restaurant. She will intercept Scarlet Maturity on his way to Balthazar.
-[X] Menagerie Witch (Shield Generator)
--[X] On overwatch on a vantage point overlooking the restaurant. Her Nevermores are our escape vehicles and her horde will assist as distractions during our ambush and escape.
-[X] Handyman
--[X] Infiltrate Balthazar early and make contact with Hiver. Scout the place, and make sure he acts with us when the ambush is sprung. Also, preferably find a place to hide in the meeting room itself.
Why give Black Swan a Shield Generator? Because she'll absolutely need it against Scarlet Maturity. Our entire plan hinges on being able to retreat to the Apiary atop Maddie's birds, and that means Black Swan needs to last as long as possible in her duel. Thankfully, she can go supersonic and even lightspeed so she should have no problems outrunning him once everyone's safe back in the Apiary.
As for the plan itself, it leverages Lady Leizi's information network to make sure Scarlet Maturity doesn't surprise us. He's 12ft tall and pretty distinctive, so I don't think he'll be in the restaurant itself when the meeting starts since that would obviously ward Lady Leizi away immediately. As such, I think 4 Seasons will play hardball and keep us in place until Scarlet Maturity crashes the meeting.
We avoid that by having Mona fight SM, and we knock Été and Printemps out with our own ambush after we gather enough information to know that they don't have a bomb collar on Hiver or something. That way, they can't interfere with Mona and SM's duel, and they won't be able to interrupt our escape either.