An idea for a new game mode

It would take place on the crystal scar, and a team would work to cooperatively work to hold off against waves of bot controlled champions until they lost the nexus at the center, you wouldn't be able to leave the outter ring, and would have turrets to help defend at first, but as you progress the bots become stronger and more numbered. possibly without items and with a progressive buff. I have a crappy image i made to give an idea of what i mean.