I'm in a multi-player game. Opponent A attacks Opponent B with a number of creatures for this purpose, none of these have first or double strike. I want to maximize how much pain my opponents feel.
Is it possible for me to cast AEtherize post damage while the creatures are still considered attacking?
Yes, you can do that. Players get priority in both Combat Damage step and End of Combat step and creatures are considered attacking for the whole duration of the combat phase. So you definitely have a window there, where you can do what you want.
Works well against Teysa, Envoy of Ghosts to keep your creatures from going to the grave... you deal combat damage, Teysa, Envoy of Ghosts 's ability triggers... you AEtherize to return your creatures to your hand, and then recast them after combat.
(Though your opponent still gets a 1/1 spirit token for each creature that dealt damage)