Parallelizable tasks can all be solved whenever (again, plumber), and all the work that remains will be in serial. Ems will be tasked with jobs on their instantiation, and will return their results to whoever needed it when their task is completed (which could just be another worker). This brings corporations outside of the realm of bosses and economists and pulls them into the realm of computer scientists. Corporations will look a lot less like pyramids and a lot more like computer programs.

This doesn't make sense to me as an objection. Some tasks are not very short and parallelizable, so you need extended serial work. And some of those tasks will profit from coordination between different minds with different skills, or different memories from earlier in the project. Coordinating those units would require some kind of communication and management.