Now that the DM World Cup has started, I think that the addition of non-mirror matchups are an awesome idea! I prefer that by a looong way.
I like the current cautious taken approach, with keeping some mirror matches + carefully crafting how the civs are chosen, so that a late-game powerhouse doesn’t dominate against a civ that drops off in imp… If successfull in this WC, DM mirror matches should in my opinion be dropped entirely in the future. 
Perhaps another innovation (for the future) could be to start games in the Castle Age? Strong military capable of destroying the enemy is still possible right off the gate, but producing units would now have to be balanced with ageing up, building a blacksmith and university, and researching upgrades. Plus civs that drop off in imp. get a stronger chance, as they don’t spend as much ressources researching expensive upgrades.
There is a precedent in AoE II for this: Prithviraj4 (and also somewhat Attila5).