I think it would be funny if they got Siri or the like to do the voice of Milhouse for a few episodes. Maybe even change them up but always obviously artificial. But say they are “exploring AI and other technologies for duplicating the voice.”
Then get another voice actor who is really good to take the role, but then Milhouse’s appearance is slightly altered thereafter. (Like a Dick York/Dick Sergeant appearance change, only it would be subtle.)
I think I read they got the real voice for this.