Battle for Azeroth will launch very soon, so I would like to suggest a new category: "Level 110 to 120"

With subcategories: "Alliance", "Horde", "Solo", "Party", etc

What do you think about this ?

The problem is it's a nice category for each character once, as in you can run the category one time, and then never again, as you will almost never level from 109 to 110 on an exact level with 0 extra xp. There's no standardized start or stop, since characters will be in different places from where they log in, and I'm not sure when in the expansion you're considered "actively progressing" and when it's filler. Plus, we had 100 to 110 for close to 9 months with one person submitting a run, and it was DQ'd because they had level 100 with progress towards the next level because of discovering Dalaran. There's just no good way to set up rules for it, and it's difficult to keep everything equal.