A DM mode isn't the place for a bizarre competitive round robin mode, it should be attempting to emulate table top as much as possible
'Should' is a key word. You have a community familiar with GM. But this idea rather new for many Larian's players. This players were rather dissapointed by GM as KS stretch goal. So I thought, They can be interested in some sort of symbiosis of pnp GM and asymmetric coop-multiplayer.
In fact, I think, Larian will make GM mod like 'developers mod' in Divinity 2. There will be launcher with 2 options. And if you choose GM mod, there will be notifications like: 'Developers are not responsible for failed script, stability etc in this mod'. And you can do anythig you want in game.