> It's pretty clear that the security models that were design into operating systems never truly considered networked systems

Andrew Tanenbaum developed the Amoeba operating system with those requirements in mind almost 40 years ago. There were plenty of others that did propose similar systems in the systems research community. It's not that we don't know how to do it just that the OS's that became mainstream didn't want to/need to/consider those requirements necessary/<insert any other potential reason I forgot>.