There is a pretty detailed technical post over on ECA that was done by werewolf awhile back. I'm pretty sure the general consensus was you can't do much. There are some benefits that particular DAC offers but it's not really upgradeable if memory serves me correctly.
However having said that converting one of the outputs to coax should be doable. As two the other thing on your wish list there's always posts about hacking the Ai-NET protocol for simple tracking/volume commands but nothing ever seems to come to light. It would be cool though
Give jc2, Kevin7909, or werewolf a holler over at ECA