For me the ultimate Ultra (Plus) would be without any analog parts and full focus on the digital handling and services. That means better CPUs, more memory, multiple digital in/out (coax, optical, usb) but no DAC or ADC.
Then if WiiM would make highend active speakers (floor standing and sub) with LinkPlay module and top-end DACs, that would be the optimal setup. Else there are many good active speakers with digital input that can be used. I really prefer active speakers with unit optimized DSP and amplifier, to standalone amplifiers and passive speakers. Let us have digital signal all the way. No need for any kind of "smart" cables.
For the WiiM Ultra Plus I would also like to see the screen extended to the full width. No need for the volume knob for me.