I would look at how the APM product implements lifecycle management as guidance here. APM deals with Ideas and Demands to indicate intent to retire or implementation of new Business Applications early in the lifecycle. There are also 3 processes in APM to help with the onboarding of new, change to existing, and retirement of Business Applications. The status / stages would be a function of the execution of that work related to changing the status.
Status of "Fully Decommissioned" would be more clearly identified when observing the status of the project (or agile Story) that is slated to do the actual retirement work. You wouldn't just arbitrarily change the status, until that work is complete. The APM roadmap view provides an indication of all related work planned, and being executed against that Business Application. I wouldn't allow someone to have a status until that work is compete and ALL environments are decommissioned for example, all related work is actually done.
The most robust way of handling this is to define the decommissioning process with a PPM project, which includes tasks like archiving data, and re-allocating hardware for example. Since there are different types of Business Applications out there, a PPM template can be tailored to the decommissioning requirements, such as those that have financial data where retaining records is important, or Business Applicants with many with dependents that need to be informed, coordinated, and migrated as needed.
Just careful of attempting to add more lifecycles with information that's not really lifecycle, and more an activity or intermediary status that comes from related work or items.
