Sure, but this approach is going to be much more complicated and less predictable than the "switch the docroot to a completely different directory" model. (e.g. you need to distinguish between asset and non-asset directories, and make a decision about how long to keep "old" assets around.) With some effort these problems can be solved, I'm just pointing out that even with a completely static site, and perfectly atomic docroot switching, you can still end up with clients in an inconsistent state.
Comments
Two phases. Leave possibly referenced assets for a while until use of cached old files has become rare enough, then remove them.
Sure, but this approach is going to be much more complicated and less predictable than the "switch the docroot to a completely different directory" model. (e.g. you need to distinguish between asset and non-asset directories, and make a decision about how long to keep "old" assets around.) With some effort these problems can be solved, I'm just pointing out that even with a completely static site, and perfectly atomic docroot switching, you can still end up with clients in an inconsistent state.