Battle of the Minions!
In Battle of the Minions, it would be a normal game on Howling Abyss or a similar map. You play the game trying to kill the enemy nexus, but there is a twist. All champions gain a new resource (to which i am going to call gems right now). They gain this resource by 3 ways, killing minions (1 gem), killing enemies (2 gems), and destroying towers (3 gems). These gems can be used to buy items for the different minions. Each champion on the team will be assigned a minion wave they can buy items for (5 champions so every 5 waves their own will show up). Because this is on howling abyss, it will be kinda hard to farm, but it is still possible.
The game mode will make champions prioritize both fighting and farming minions. For example, I would say 1 gem would be equal to about 250 gold or so. Therefore, if u wanted to buy an item for one of your minions, such as infinity edge, then u would need to collect about 15 gems.
Hope u guys like the game mode, leave suggestions in the comment and remember to up vote if u like :)