I don't think there are any true medium size corpos in the entire industry. Sure, you can isolate stuff by noombers ex-JP but it doesn't account for the fact that HoloID, HoloEN, and NijiEN all have massive inbuilt advantages for things like merchandising and brand collaborations. Brave is still pretty small when compared to Cover and Anycolor but I guess they would be the """closest""" to medium size. As far as corpos go, the industry is a duopoly with a few much smaller players. Compared to another industry, I don't think many people would consider companies like Embraer, Bombardier, UAC, and COMAC to be medium size when they're playing in the same sandbox as Airbus and Boeing.
None of this categorization matters anyway but it's interesting to think about.