If taking the space from another room does not interrupt the flow of the house or leave the room in an odd shape then it would be a great idea. Having a separate tub and shower is the ideal layout for a master bath but if you have to force it in then it is better to keep the tub shower combined, leaving room for the bathroom vanity. It is also common to not have a bathtub at all in a master bathroom and instead have a large shower with glass enclosure and multiple shower heads. Removing the tub is Ok if there is at least one bathtub in the house.
