@pulkomandy The #msdosfs (#FAT) driver seems to quite healthy, receiving regular changes bringing bug fixes, cleanups, and improvements. I've not heard of any plans to rewrite or remove it. It is a solid piece of software in #FreeBSD and it's going to be maintained for a looong time.

You could also send your questions to the #hackers mailing list:

https://lists.freebsd.org/subscription/freebsd-hackers