For me the most important feature would be
USB-Type-C data+power connection, via supporint USB-PD (Power Deliver).
USB PD's first iteration could already feed any kind of DACs with enough power (~100W if I'm not mistaken), however with USB-PD 3.1 specs allowing 240W power delivery I really don't see the need of those bulky power cords on my tidy desk.
This also applies to a low-moderate powered amplifier as well. With daisy-chaining lol.
I was already wondering why my E30 has to occupy 2 USB connections on my HTPC.. (okay, the power can be any other kind of cable too), why couldn't I just feed the DAC via 1 cable and problem solved for data and power 2-in-1.
I have no issue with a classic DAC (or amp) design holding a fully fledged 110V/230V AC power supply inside because we don't always feed a DAC via PC (see Network players, Raspberry Pi-s, etc)... but pleeeassse add the possibility of USB Type-C input with PD support so in case of I'm somebody who doesn't give a f* about all those snake-oils I can feed the DAC with power + data via 1 single USB Type-C cable, from my motherboard's USB-C (PD) output. Or from my new-gen laptop, same..
All other aspects - I mean mainly my ear+brain complex - are already satisfied, even with the E30. (I love AKM).
Cheers