I believe that there is another user on here who is doing that. If you don’t have the optional RTC battery connected I would suggest that, to keep the settings when the machine is off of power.
The blue/red situation needs looking at so we can consistently boot when the mainboard is alone. It will probably wish to throttle as the fans are not there, but it should boot.
This might be my next EC investigation, mod that I look into.
I already have a similar case.
When I use the efi “ectool reboot rw” to get the EC running my modded version, if the psu is not present, so only battery present, it reboots, if the psu is present, it switches off, and not reboot.