your assumption is not true. On the level of operating of FC (block level filter driver) there is no information of the file that might be written or read, FC deals only with numbered "data blocks" relative to the partitions 1st data block or disks 1st data block. Maybe FC knows something about the filesystem underneath. But your initial feature request was: "Exclude specific files from being cached". And this would require exact information about every file that is currently in operation by FC *AND* the files corresponding data block (numbers). This would require far more than a block driver. Anyway your requirement is possible of course - everything is possible.
The fact, that FC works as a block level filter driver is one of the major advantages. Example: As we know FC works well with encrypting filesystems like Truecrypt or NTFS enryption (EFS). How can FC be aware of a specific file on an encrypted filesystem when the encryption/decryption takes place in an upper level of the operating system and the encrypted filesystem is represented as one large file on the storage?
I´m very happy with the general architecture of FC as it leads to a fast, reliable solution. Everything that would require more checking of the content during operations like "to which file does this block belongs to" would have an impact on the performance.
In addition if FC would know which files is being written, it should be aware of much more as the MBR. And it should know the details not only of NTFS, but also of FAT16/FAT32 and any other filesystem (Truecrypt, EFS, NTFS compression) that might exist on Windows.