This question is answered in Linux-NTFS.org's info page:
kernel_driver trashed NTFS volumes. It created a bad name for Linux support of NTFS."
"So the current driver only supplies a feature once it CAN NOT TRASH [the users'] system."
"So basically, there is a lot to be done, and only one [active] man to do it."
It's a time issue, in the end. As you pondered, yes, all knowledge needed for NTFS write support has already been gathered and reverse engineering is not required anymore. It's pure implementation that's left to do but it takes a lot of time, based on the quoted facts.
I don't know what your reasons are not to use
ntfsmount, but if you absolutely need the kernel driver, you can do it yourself (open source ftw!) or support the original author(s) to do it faster.