I guess if you are trying to emulate a server, you are better off using a server style of file system, probably derived from Nix, that both sides can read and write. FAT32 isn't really designed for that. It does limit how complex the directory structure can be, but if the structure actually used isn't that complex, this is not an issue.
Even if it works now, it will fall over sooner than the other options, as entropy on the structure occurs, it becomes more complex over time. That process might never complete before a system fails elsewhere, or it could happen rapidly, depending on how often the contents are altered. The universe could in theory die before the directories overflow.
Myself, I would want to put a hardware write protect option in there somewhere. You don't want it to change very often, I guess. Not sure about that, but if either side can trash it spontaneously, then obviously you are doubling your risk factor. Might be too late, and let's face it, double "almost infinitely zero" is still "almost infinitely zero" so it's maybe not much of a real factor.
I just like SD cards over USB thumb drives. For this sort of thing, anyway.
