It'd be nice if you could mark a file for deletion, and it would be deleted during idle time of the hard disk. After marking a file for deletion, it could be rendered inaccessible until you unmark it. i.e., it would be locked. When the processor and disk isn't in use, it would be deleted. This would be nice for when you want to delete a large directory, but don't want to sit there and wait while the disk is thrashing.
You are asking for a fairly significant change that even if it were feasible would effect every part of the system in unpredictable ways. This is not something that we will implement ourselves. If you think you have a workable plan, then propose it to upstream kernel.org.