May be some other solutions for storing IDs. Ex - storing a small amount of metadata in the filesystem
while storing the key-value storage in a block device.
There is not a big problem to have several block devices during a maintenance. LVM may be used for this purpuse. It allows to allocate new logical block volumes and delete them. LVM is also useful for making RAIDs, striping, snapshots and so on.
I think the main advantage of block devices is not to waste extra memory for filesystem cache. OS behavior is unpredictable when there is a large iops volume through this cache.