Ah, but the show already has perfect setting/excuses for all of those character's not to be present. Odo hasn't returned home yet - he is still with the Founders. Sisco likewise is still with the Prophets. And just take the DS9 documentary's season 8 pilot storyline - where Captain Nog appears through the wormhole with an urgent warning just to have his ship explode. Can't think of a better way to go out then have Aron a captain on his own starship going down with the ship while bringing a saving warning/message to his friends and allies.