I believe AM only blocks assets with a status of "Deleted" from showing up. I think workflow will be your only solution.
This is request for enhancement for :
When a ci is disposed off or deleted the customer is asking that the related cis should also be disposed off or the customer must get an option wherein he can ask for the related cis to be deleted .Eg when a computer system is disposed off the related memory , hdd should also be marked as deleted .
Agree with sydney. I would say disposed CI's have to be deleted. as they are no longer needed to track.
where deleted CI may come deployed after some point of time.
Please get back on this if above information was some help to you