There is a option that have been on my todo list, that will probably make it in the next version, to only sync new/modified files from the source folder (compared to previous sync), with no replacing of missing remote files and no sync of deletions.
This option, used in conjunction with the timestamp folder option, will do what you want.
If used with ordinary one-way syncs, it will enable you to delete files in the target folder without them being synced again, unless the source file gets updated.