Sorry, I was abusing the terminology. When I mean "0.5 FTE", I don't mean (necessarily) that you'd be hiring someone to work part-time. What I am saying is that if you have an IT team, the time that should get dedicated to this particular service should be at most 20h/week.

Presumably, your IT team will have many other projects to work on, some of them will be on-call, some of them will be on vacation, etc, etc. But when allocating the resources, I'd guess that 20h/week is plenty to such a service, even for a corporation of thousands of people.

Does that help?