I was talking about this with my squad last weekend, and I'd like to see a stage that incorporated sprinklers.
A layout with similar platform height differences like Mahi Mahi, but maybe a bit more square like Urchin Underpass. Anyway, there would be one sprinkler close by each of the spawns, and then one larger sprinkler near the middle. Similar to how the sub sprinklers are destroyed, to get one of the sprinkler to activate you need to deal a certain amount of damage to it. And obviously once your team activated the sprinkler, it sprays out your color ink. To initially start a sprinkler it'll take the normal amount of damage to destroy a sub sprinkler, but to take one over (change the ink color from the enemy's to yours), it'll require double the damage.
A few ideas I was thinking about with this was if the permanent sprinklers would deal out more damage, as well as if the sprinkler in the middle would have a wider range (and possibly deal less damage than the sub-sprinklers/ spray at a slower rate). For the last minute of a match I was also kind of thinking about maybe having the sprinklers turn off or spray water instead? Possibly making the last minute more intense and crucial.
Or maybe a stage that involves some large rotating platforms? Like the platform flips to another side after 15 seconds or so allowing both sides to be inked, and maybe some surprise splats from people hiding in the ink as the platform rotates. :)