Use posixovl to save changes
Is a controversial idea, but good: Use posixovl to help to save changes. This solution allow write POSIX files in FAT32 filesystem without errors or limitations (symlinks works, for example). This idea is good because allow save changes inside a directory insde USB key root without a space limitation (a problem using a file). Eg.: USB key is 4GB size. If use a file, for exemple, 256MB, The user only can save changes and files to 256MB, but using posixovl he can use 4GB (less distro size)! And access his files (but a symlink or mount -o bind make the same). Sorry my english. Thanks.
Marcos Henrique Esteves Barbosa