May I take the opportunity to bump a previous idea - Tame Titans
Every time your alliance defeats a Titan, you have a x% chance of capturing it.
These are kept under lock and key until the next war.
Then the leaders can select their titan of choice.
During the war, same drill, war bonus bar fills up and then
BOOM - TITAN STRIKE - death from above, fire and brimstone (or ice, or the weird, glowing purple balls)
It’ll need some balancing, the hits would be much softer than the titan battle, but proportional to the level or your captured titan.