At least the most complex design aspects are taken care of on the compute module.
Finding an open source host PCB design that is close to your design goals, which you might be able to modify, would be a real time saver.
The previous post on First Compute Module Host w HiFi Output
that outputs audio through a hifiberry-dac driver is one example.
This more basic board selling for $130, has a “Customize Board” feature on the sales page, using Upverter.
This guy seems to be monitoring compute module developments in this database.
Jeff Geerling 's blog
You may have seen his Mar. 23 article:
The Raspberry Pi can boot off NVMe SSDs now
(His boot benchmarks show little difference fiom SD card)
.
Update on this little Compute4 Module sized “Backpack” board with 40 pin gpio:
EU approved, they are offering some copies for early users, (it has a known headphone distortion)
https://twitter.com/i/status/1382830258056015879
---- A hardly related curiosity ----
I was just looking at the hobby board line at Sparkfun, that includes little MicroMod processor modules using M.2 format connector similar to what NVMe boards use (‘E’ keyed with non standard mount spacing). Not sure when it’s a cost effective approach, perhaps when doing in context benchmark comparison tests for a new product design. (Looks like their connector uses a ‘universal’ GPIO format). Available processors:
Artemis
nRF52840
RP2040
SamD51
ESP32
STM32
They have 7 different special purpose Carrier Boards that accommodate these processor modules. (One enables the RP2040 to output HDMI)
(You can get 5 - M.2 carrier sockets there for $6.95)