How should DJ Fenris be played?
You can't have ID cards in your deck;
so any ID hosted on DJ Fenris is not part of your deck, it's similar to Rebirth in that regard.   

You don't have to bring all eligible IDs, only ones you ever plan to use.
You also don't have to show which additional IDs you have to your opponent until you actually play Rebirth or DJ.  

You are still limited by the IDs legal in the format you're playing, 
so for Standard; Noise and other rotated runners as well as draft IDs are out.
Your faction will limit choices too.