I'm in preliminary research mode to plan a NAS build right now myself.
Though I'd like the convenience of hotswap bays, I've read that the several of the available NAS cases (including my front runners the CS380/381/382, U-NAS NS-810A, and Jonsbo N4) have cooling issues. And while the Jonsbo N3 looks better for cooling, there is no way I would use essentially rubber band handles to pull the drives out of an N3 case (which is what they send you and expect you to use).
I'm seriously considering just picking up a Fractal Meshify 2/2XL case, then popping an eBay sourced used HP Z420 or Z820 motherboard, used Xeon CPU (or two, for some of the Z820 boards), 128 gigs of used DDR3 ECC LRDIMMs, and an IT mode LSI HBA card in it and call it a day.
Honestly, I'd really, really like it if Fractal would do a modern day update on the Node 804 series. I know you can still get them new from a few places, but I hate the thought of building a NAS in a design that old and then not being able to get parts when I (inevitably) break something after they (inevitably) finally have totally discontinued it.