There are a zillion different products for system integration, and that’s fine. But now I have been at different big companies that actually have the opposite problem. They need system segregation! Take for example an airline company I worked for. They had around 250 different IT systems, most of them legacy systems in different stages of decomposition. The big challenge was not to integrate the new systems with the old, but to isolate the old systems that needed to be phased out or replaced.
The systems need to be segregated so we can put up well-defined and modern interfaces between them. Unless this is done, replacing the old systems will be a nightmare.
So where are the processes to accomplish system segregation? And how would a toolbox be composed to accomplish this? Do we need new roles, like a “Legacy System Surgeon”? 
Good point!
Usually when System Integration is discussed a “before” and “after” picture is used. The “before” picture shows a number of systems connected in a spaghetti-like fashion. The “after” picture shows the same systems in a proper row or circle connected through a node or bus or something. The “after” picture illustrates System Integration but System Segregation is what happens between those pictures (and that is the difficult part).