I do see this being beneficial in co-op, which I think is where the purpose will best fit. Communicating over voice can be hard for people and I think this is a good augment for communications.
For maps with hastily drawn floor plans, will those appear on the tablet in said hastily drawn form?
You better believe it! We even have some outdated floorplans, which will be fun. All levels will have one though, either leaning towards highly valuable pre-game information or towards worldbuilding and storytelling, depending on what serves to provide a cooler experience.