Dunno if can help, BTW ReactOS devs apreciated (and adopted) it:
[quote]FullFAT is a fully featured FAT 12/16/32 library. It features optional LFN (Long File-name support)
Fast and Efficient with Low Memory Footprint
Scalable from Embedded Systems to Desktop OS’s
Thread Safe
Multiple File Open
LFN Support (optional).
Fully Featured
Optional Caching
Safe Caching behaviour
Customisable Caching behaviour
Multiple & Single Block Reading
Platform independent, no assumptions about Endianess
Easily integrated into current OS’s and Frameworks
I have begun writing this library because I am dissatisfied with the many Free FAT implementations, the ones that implement LFN’s are bloated and slow, like the FreeDOS driver. Others are lacking in features, buggy, or no longer actively developed.
The aim is make a really high-quality FAT driver that is flexible for many different needs, and do it better than any commercially available option.[/quote]
http://code.google.com/p/fullfat/
It always depends how easy it is to port the driver, and how good the native FS driver is as well 
Interesting, but the FullFAT’s licence (GPL) is not compatible with the Haiku’ licence (MIT)