My friend's father did

Cover up pipes, lay down flooring and walling, turned into 4th bedroom (big family) and play room for kids

Obviously did a lot of work in order to make it vermin free. However it is very hot and air conditioning is expensive. This is because the attic serves as an insulator for the rest of the house. It gets extremely hot up there, hotter than the rest of the house. The kids didn't mind but then they're young.

Malaysian houses tend to be badly insulated as we don't live in 4 season country where loss of heat means death...