Tower Buff : Sterak's Bulwark
In the past, towers had interesting mechanics to make them more defensible (the ally regenerating shield namely). This turned out to be something that prolonged games a bit too much. I personally think that the issue was that it worked on a permanant basis.
My idea, to make towers not fall like dominoes, is to give towers a
Sterak's type enhancement where:
"Upon taking 1500 damage within 10 seconds, this tower is shielded for 500 damage and gains 100% attack speed for 7 seconds."
This change would do nothing in prolonged sieges, but in the case that a team is aced, it should help prevent the other team from killing 4+ towers before respawn. This change would also encourage split pushing to prevent too much damage stacking on any single tower.