Definitely do the direct mount inside the jail, not via SMB, you will just need to make sure your permissions are viable. I generally do this by ensuring the user inside the jail that runs the software is in a group that has writable permissions for that folder. For example, I have a dedicated dataset for downloads, with permissions like this:
Code:
# ls -dla /mnt/Jails/Downloads
drwxrwxr-x 4 xxx sharedfiles 4 Feb 15 06:05 /mnt/Jails/Downloads
Note the group "sharedfiles" has write access to the directory. You do need to be careful with permissions, as you (probably) don't want everything writable by everyone, but regardless of how you make files/directories available to the jail, you need to care about the permissions (ie this is true when using a CIFS/Samba mount as well).
In my case I want multiple jails to have write-access to this folder (ie downloads then post-processing).