What functionality would the ideal mainboard for a cyberdeck have?

Raspberry Pi's are amazing from a cost, form factor, and GPIO perspective, but they're a little underpowered to use for a PC. I'm currently developing something that may be an interesting higher performance alternative, and I wanted to check what folks here would find useful in a cyberdeck mainboard.

Low stack height? Integrated cooling? Connectors along a specific edge? Specific types of I/O? Integrated battery support? I'm interested in hearing your ideas!