You can mount drives as folders in an NTFS volume too (just like on Linux). To me, however, it does not solve the problem of having the free space divided into many drives (so I have enough free space for a new series, but I do not have enough free space on a single drive, so I have to write 2 episodes to drive 1, 3 episodes to drive 2 etc)
Anyway, if you use JBOD and one drive fails, it is the equivalent of a lot of bad sectors appearing on a single drive. You will lose all files that are in that drive (and all files that are partially on that drive). However, if the drive that failed, contained the filesystem information (MFT on NTFS), then you will lose all files.
However, I found
FlexRAID. While the main function of it is o create a RAID of HDD image files, it also has a "flexraid-view" function, which creates a new drive letter, which combines all selected drives, that is, imagine I have two drives with these contents:
E:\anime\ep1.mkv
E:\anime\ep2.mkv
F:\anime\ep3.mkv
With flexraid-view I can create a new drive letter that combines these drives, so I get:
G:\anime\ep1.mkv
G:\anime\ep2.mkv
G:\anime\ep2.mkv
The only downside of it is IIRC that this is read only, if you want to write a new file, you have to find the drive with enough free space manually, otherwise flexraid will just write it to one drive and fail if that drive does not have enough free space.