Right now when trying to replace a deleted post, the site returns the error message Post is deleted.
I assume this is intentional, however sometimes there is a valid reason to create a post replacement for a deleted post.
For example, if a sound edit version of a post gets deleted because the video has worse quality than the original silent version.
In this case, replacing the post with a corrected version would make sense, as this would eliminate the reason for the post deletion.
Like post #5247368, which is the post I've tried to replace before running into this issue.
I don't think there is really much of a problem with allowing users (with replacement permission) to create post replacements for deleted posts, since these have to be approved by mods anyways.
So there is not much of a vandalism opportunity there.