The DR-DOS/OpenDOS Enhancement Project

I was not able to find any specifications on the filesystem
structure of exFAT; without this info it would not be possible to
implement it.

Also, it is safe to assume that despite the name, it is incompatible
with all previous versions of the FAT filesystem whereas FAT+ is at
least downward compatible with FAT since it only uses six additional
bits in the directory entry.

Cluster sizes of 32 MB are probably not the smartest thing to
implement in DOS, either, given the fact that even much smaller
sizes are notorious for wasting a lot of disk space for short files
and many applications have difficulties even with 64 and 128 KB
clusters.

I think interoperability with other OSes is better served by FAT+;
after all, exFAT will only be supported in the latest versions of
Windows and it is unlikely that anyone will be using those along
with DOS, anyway.