I think squeezing all that in and have it passively cooled to boot is going to be a tall order. Especially if you want PoE to boot. I wouldn’t count on something like that appearing any time soon.
Fanless cooling with decent cool block on the switch chip and on the SFP+ cases, would just be proper thermal design. The sfp+ modules need at least as much cooling as the switch chip! Nothing more than that!
Twelve in state eight 2.5 ports seems possible to me as well. Also at this moment in time.
Note that I used to have a CRS317 with the same bad thermal design. Noisy fans cooling ^nothing^. The cpu cool block, was not cooled by the fans, and the SPF+ modules also not. So also not. So lots of improvement options in regard to thermal designs
I’m posting this here because, while the Zyxel looks nice, I don’t know that it will fit well into an ISP’s network, and I know a lot of ISP’s looking for a switch that meets your topic and OP.
I have a couple of the Hyconext switches. While they have fans, they’re pretty quiet unless you’re putting a 100W or more through them. The fans look like they could be replaced with Noctua fans.
They can handle lots of passive POE (MikroTIk, Ubiquiti, Siklu, Cambium) at both 24 and 48 volts. They have AC and DC/battery models.