I agree, I’d like to see a simple 45HL caddyless backplane case in this space, although I’m not personally in the market for one now, I would have jumped on it 6 years ago. If you went with the motherboard they’re using for the Home Workstation (Asrock H670M-ITX/ax), it only has four SATA ports, so one way to get around that without using the PCIe slot is an m.2-to-SATA adapter card.
Asrock Rack has an X570D4I-2T
https://www.asrockrack.com/general/productdetail.asp?Model=X570D4I-2T#Specifications
Which would give you onboard 8 SATA and 10G NICs, but only VGA output, so you’d need a low profile GPU or something if you wanted higher end graphics output. Note you might have to pay more for a board with more SATA or faster NICs on board, but it also means you don’t have to buy those seperately as PCIe cards.
Here is an article with some ideas;
https://nascompares.com/2024/02/09/the-best-m-itx-cpumotherboard-combo-for-your-nas-build-2024-edition/
Back on the case, the Silverstone CS382 has 8 hot swap bays but is a bit larger, accommodating Micro-ATX motherboards, which may be good or bad depending on the form factor you’re after. Also, the Norco case that I had used before they went out of business, the “ITX S8”, now seems to be marketed on Amazon and Newegg by some company named KCMcconney;
https://www.amazon.com/KCMconmey-Internal-Compatible-Backplane-Enclosure/dp/B0BXKSS8YY
One thing I liked about it was that the backplane had two SFF-8087 connectors rather than the Jonsbo and Silverstone that have 7-pin SATA data connectors for each drive. So, although hot-swap, they don’t really reduce the cable jungle of the build much. Note that these cases may require special power supplies, so pay attention to that. I think the Jonsbo wants an SFX max 105mm and the KCMcconney wants a FlexATX.
Anyway, my point wasn’t that you should go out and build a PC if you’re not into that sort of thing, only that there are a few cases around that have 4- and 8-bay hot swap backplanes if 45HL can’t bring something to market in a timely manner.