In terms of i/o capability, the specs of the Madiface XT would work well for the purposes I'm proposing.

But the point is that I want open source drivers, and open source hardware! I don't want to depend on the health and the priorities of a commercial entity. I want to be able to inspect the driver software and contribute towards perfecting it!

Compared to, say, GPUs, the needs of multichannel digital audio i/o are modest and not changing very much over time.