I know I can use the breakout method as you call it, but I really thought tool would be able to handle this very basic interface. Its really just like an sram interface with two chips but no address lines. Why is that so special?
For my two A/Ds, I added a tri-state bridge to the system and then two instances of a new tri-state slave component with clk, reset, cs, rd,wr,data. After generation I see it was smart enough give me just one data bus, but not smart enough to give me just one rd and one wr. Maybe I do need to stick with one component, but then it looks like I need to do address decode for the two chip selects, and I am back to the old 'interface to custom logic' method.