We're not measuring quality of recording based on just bitrate, are we? Moreover, are you sure you can discern down converted file from original in blind test with aligned volume?
R-2R ladder DAC is worth giving a shot and it could play very well on behalf of Cayin's innovative approach. Try to bring up this topic for discussion on a meeting.
Hmm, you have a point here about space and stuff. However, for portable solution we can choose R-2R ladder DAC that is not too power hungry. Here is an example of alternative custom board for Hifiman HM-603 based on AD1866R in balanced option.
It doesn't generate a lot of heat, 6 hours of play on default battery.