Why 16, when you already have ref.design for 8, and 8 is easier to cool...
Even when you think about immersion cooling, if enything goes wrong, your whole chain (16) goes offline...
Wouldn't it then be smarter to stick with 8 ?
16 was just a number I pulled from thin air

As for the technical challenge: with the experience collected so far, I'd say once you have an 8-chip chain working, it is not a huge step to move to 16 chips. At least from the A1 side, I don't understand the DCDC part of it to state it would be easy.
The immersion cooling idea follows DaT's approach
here, where due to the high costs of the fluid it is essential to stuff as much hashing power into as little volume as possible. I think one could get a 4x4 A1 matrix onto a 10x10cm^2 PCB and stack them with 1cm distance. Resulting in a 6kW burner in a 1 liter cube.
That would be more of a fun than a serious project and I proposed this to be added as a challenge for Bitmine's planned design contest - which for obvious reasons was put at the back of the priority queue and might never leave the announcement phase

Takers? I'd supply the chips and the fluid.
Ice Wasp is something we are keen on doing... just need to get our Wasps finished first.