Passive air flow would be best as the case fan should draw enough air. Since these are 7mm in height, only SSDs will fit and they typically have much less heat than traditional drives - I believe.
A minimal sized chassis with a focus on storage. Ideally, it would fit a mini-ITX board like Supermicro's X10SDV-TLN4F and a suitable HBA for connecting the drives. Air flow would depend on how I end up mounting your product. Since I haven't found a suitable chassis, I can't speak towards air flow. But for the needs of a small business BDR box, I think traditional front-to-back air flow would work.
However, if I wanted to build a higher density chassis, using your CP015 or CP-014, I'd look to mount the drives vertically and this would require lateral (side-to-side) air flow.
If you are allowed and if you can see my email address, send me your email and I'll give you more details of what I've been working on and why. Or, I'll see if I can send a PM via this 'forum'.