First opportunity to attack those on revenge list
I'd like to be able to actually revenge players on my list. As it is, it's highly unlikely to be able to revenge someone. If a player attacks you with a guard, you can't revenge them right away. Same if they attack with a shield, losing a few hours. So, unless you stay online as long as possible, constantly clicking the revenge button, you're odds are slim. Even if you diligently hit the button once a minute (who's doing this, really?), odds are someone else will attack them once their shield/guard runs out, and they'll get another. It's really only by chance that you can revenge them.
To fix this, I think there should be an option that allows you to revenge an attacker (and all those who the player attacked, in say, the last 24 hours). These players (on average, a dozen, maybe) would get a notice once the attacker can be attacked that they can revenge. All others would be blocked from attacking for, say, 15 minutes. Allowing those who can revenge an opportunity...among those, the first to attack is "first come first served". This would increase your odds of being able to revenge by a lot.