User controlled storage devices existence
To answer your questions in turn


"Can storage devices performance be maxed out..." - This very much depends on what you want to do. If you're using your storage as a block device for a filesystem like FAT32 or NTFS. The lack of the FTL will make things 
considerably slower: Imagine you edit a file and change a "1" to a "2". With an FTL, a spare pre-erased block will be allocated and your new data written there. Without the FTL you'll need to erase the original block, wait for the erase to finish (very slow), and then write the data. The other issue you'll have without an FTL is that you'll need to make the next layer up aware of the bad sectors on the flash. However there are use cases where not having an FTL makes sense (eg with filesystems like YAFFS)
"Are there any such devices...": Smartmedia cards are just raw nand flash chips with the pins brought out to pads. But a typical USB smartmedia reader will implement the FTL. However there are/were devices which used them directly.
"How practical...": not really practical for the reasons mentioned above. Early android phones used raw nand and YAFFS, modern ones use eMMC with an FTL and (usually) an ext3/4 filesystem.