The difficulty don't change anything,it's a unique difficulty

Hi everyone ! Why don't add new categories ? Like Casual any% (hard too) Normal 100% (do all mission with bonus objective) On WoL/Hots/Lotv/Nova ?

And i've a personnal question to ZPR,for WoL,the category of Any% no production unit,we can play on any difficulty ? We can switch it in the run ? Do you think it's possible to add this category for Hots/LotV and Nova too ?

Sorry for the bad english,i try to level up ^^'