IMO all in all the Unmatched is a great board. It’s really nice for RISC-V development. PCI-E and USB added a lot of flexibility. A lot of linux software could be ported, thanks to this. As for a future board,
Agree with regard to the cooling fan. This was a pain for both the Unmatched and Unleashed. Please install a non-noisy one by default 
I think RAM sockets make sense for high end servers, where one might install 256+GB of RAM depending on the application. But for what is essentially a SBC 16GB hardwired is plenty.
My foremost wish for a future board would be stability under high loads and long term use without resets. E.g. I’d hope Intermittent kernel oops under heavy load and the USB HID connectivity issues USB Disconnect no longer occur.