slapping such a capability onto an astromech (When defending, before the "Modify Attack Dice Step", you may spend one of your focus tokens to remove a focus token from the attacker) would
1.) limit the impact of a torpedo scout list's incredible alpha strike
2.) force imperial aces to think twice about attacking your ships, as they risk losing their defensive focus
3.) give the VERY defensively challenged 1 agi Y and ARC a much needed bit of defensive tech (1 agi when focused is pretty naff; better to spend the focus to limit the enemy's offense)
This is an Astromech I could really get behind...