I use drivepool for some time now and i am quite happy with it.
One thing I'd really like to have - since I use a lot of sample libraries for making music - would be a SSD read cache for the pool - something that works like the fusion drive of Apple where often read data is transfered/doubled on the SSD for better performance.
Something like the adaptive caching for your clouddrive.
Could we have a caching plugin like that at one point?