As a few others have suggested, the best method for supporting an approval process for creating or updating a CI is through a catalog request.

As for decommissioning a CI, that depends on whether you mean retiring a CI or something else.  You can retire a CI using Data Manager which has OOB support for approving the retirement of a CI via a task.  The only gotcha is that Data Manager uses a policy-base approach that targets CIs that meet specific criteria as opposed to something that's driven by a user for an individual CI (e.g. an action on a CI form). 

The main advantages Data Manager gives are that it's automated and it supports retiring the CIs that are dependent on the CI being retired, preventing orphans from being created.