Remember a few things:
Once you have clicked on “Save Squad”, you can not change planes. Also, the planes will remain as they were when saving the squad. Upgrading any plane will not make any difference.
The same holds for brobots or devices. No upgrade will take an effect. You cannot even equip other brobots or devices. Then ones equipped when clicking “Save Squad” will continue to be equipped until you reset the raid.
Note also that devices equipped i an assault raid, will not be available in Black Box. These devices are release only when raid is reset.
You can bring six planes, and will play up to five levels. In every level you will encounter 3 minibosses, 3 long waves of enemies, and one major boss.
While not having many fully well developed planes to select from, you will just have to bring whatever you’ve got. But you will see that many of the planes do very well. Queue your weaker planes first, and try to survive an entire level on just one plane. You will need your strongest towards the final levels. Or place boss killers towards the end, and rely on Laserbite and possibly Defender earlier during Assault.
An early setup of six planes, which you can collect fairly quickly (all planes available no later than level 50), and stand a fighting chance of taking you through entire assault, even if the planes are not fully developed would be: Defender, Laserbite, Blitzer, Katyusha, Greataxe and Flamer. (Of course it is possible to go through assault with even earlier planes. But it will be a struggle.)
Brobots? At least by level 50 you will definitely have a decent Menace. Pair it with something with both a good screen clear and boss kill, like Nayad (though the screen clear is not the best), Beetle or Nicolas XXS.