I think it would be great if the apartment got a full renovation much like the hotel exterior did. It could include important upgrades and would include Asterion renovating his room to match his new equal status. That way they still have their own private spaces. Would make for a cool "MC R&D project".
Also while his room might be small it might be the way he likes it. Asterion mentions that most people do not share his definition of cozy when visiting the first iteration of the hotel. If he did renovate his room I wonder what he would change?