The "bigram rollover" is key to reducing the number of key events, and the added bonus is that it should help ramp up the steep learning curve with getting the right sequence.
I am also investigating some sort of phonetic/bigram mapping system (maybe similar to the plover/stenotype system), seems it's the way to go, as shorthand seems to solve the main issue with chording which is high number of key events for a single output.
I am actually looking for help designing the mapping as explained above, it seems we have very similar ideas, perhaps we can collaborate?