Here is a list of people who could take on the mantle of the Bat if the entire Bat Family were out of commission due to a mass attack.
Scenario: Before or after the Bat Family was attacked, he could have been fired or on vacation to be able to have time to be Batman.
Skills to be Batman: detective, police training
How the suit would be different: not much, just a full face mask
Question- Vic Sage
Question is just a poor Batman
Skills to be Batman: detective, martial arts training (mild)
How the suit would be different: no difference
Green Arrow- Oliver Queen
Green Arrow is just an archer Batman
Scenario: GA would go to Gotham as Oliver, and Speedy would pose as GA for Star City.
Skills to be Batman: martial arts training, tech
How the suit would be different: he would add Queen Ind. tech to the suit along with Wayne Ent. tech.
Deathstroke- Slade Wilson
Scenario: No one is available and Batman is desperate, he pays Slade to be the Bat, and extra to keep casualties low.
Skills to be Batman: superhuman strength, speed, agility, and durability; increased brain capacity, martial arts training, military training
How the suit would be different: eyepatch, jaw cover, energy lance, guns