This is a really interesting product! Like ari2asem, I'm also looking for an external/enclosed solution. The dream, and I have no idea if it's possible would be something like this, enclosed, populated with the 4 x M.2 drives per slot while somehow being all tied together with a Thunderbolt 3 ports for daisy chaining. I'm so encouraged by your pricing, but I imagine my dream solution would require a SAS port card and enough cpu and memory to run it, driving up the cost. Still, one can dream.
Please forgive me, as I've only just run across your products and haven't fully learned their capabilities. Are these 5.25" cages/slots supposed to be compatible with NAS and DAS products? The reason I ask is that, up to this point, I've been looking at the Areca Thunderbolt DAS solutions. Probably the 12 bay, with the 24 bay being the dream. It would be nice to be able to use your M.2 bays with a product like this. https://www.areca.com.tw/products/thunderbolt_8050T3.html
At any rate, keep up the great work and I'll keep my eyes peeled.