We implemented a business rule query that checks a new field "Active" on cmdb_ci. Within the BR-Q we check against roles to either show or not the CI that have Active=False. This way Admin, Config Managers and Auditors can see inactive CI's, but 'normal' workers don't see them anymore. 

Be aware that some Business Rules, CMDB Health, etc. will/can be impacted by this, since those might also not see all CI's anymore.