The CM4 footprint seems somewhat popular. With a range of compute modules (https://community.twistedfields.com/t/alternative-cm4-modules/334) available
This Kicad project exists https://github.com/antmicro/arvsom
I suspect a high-performance version Amlogic A311D2 (https://www.khadas.com/vim4)? might be popular
You could then optionally produce the Gumstix carrier: https://github.com/gumstix/PKG900000001400 Maybe call it Pumpkin pi or something.
Perhaps a Crowdsupply would give the confidence/time to work on it? https://www.crowdsupply.com/search?q=cm4
Or the T-Head TH1520 quad-core Xuantie C910 looks interesting
https://liliputing.com/sipeed-lichee-pi-4a-is-a-modular-risc-v-mini-pc-with-up-to-16gb-ram/
https://www.cnx-software.com/2022/12/14/sipeed-lm4a-t-head-th1520-risc-v-module-to-power-raspberry-pi-4-competitor-and-cluster-board/
I'm increasingly into the Beaglebone footprint.
If a CM4 carrier existed for that it may even be popular?
(https://agroecologylab.org.uk/wp-content/uploads/sites/2/2023/01/cm4.png)
There would be several open hardware capes that could be used for it.
A UEXT one would be fairly trivial to create
(https://agroecologylab.org.uk/wp-content/uploads/sites/2/2023/01/beagle-uext.png)
I have some slightly mad ideas for using the Beaglebone footprint/pinout as a platform for Microcontrollers based on the Sparkfun Micromod system (https://agroecologylab.org.uk/open-hardware-electronics/), but that's an aside
Or maybe a CM4 variant of the iMX8MPlus (https://olimex.wordpress.com/2022/01/25/imx8mplus-som-is-alive-and-boots/) now that it's in stock (https://www.digikey.co.uk/en/products/detail/nxp-semiconductors/MIMX8ML6CVNKZAB/13897887?WT.z_cid=sp_568_buynow)
This Ubuntu exists (https://boundarydevices.com/ubuntu-jammy-jellyfish-22-04-unified-image-for-nitrogen8-boards/)
https://www.crowdsupply.com/ov-tech-gmbh/pi-mx8-module