The passenger door latch is operating as designed, so I guess I can claim some degree of success!
It’s been a frustrating process, but the passenger latch now opens with both the outside and inside handles. Before I install it permanently, I want to remove it to adjust one end of one cable, so the latch opens slightly earlier in the handle travel. Right now it releases in the final quarter inch of movement. At least the inside handle works beautifully and releases at half-travel!
The good news is that the oddball design functions quite well, but the bad news is that the hardware is seriously crammed together in a small space and I’m concerned about possible chafing of the cable jacket with time and normal vibrations from driving. The contact is bad enough that I’ve decided to make additional changes in the driver’s side actuator to reduce the package size and allow minor cable rerouting. I’m a little worried that those changes could increase the cable pull-force too much, but I have to give it a try since the driver’s door will require more reliability and built-in adjustments than the passenger door, which does not get as much use.
For now, I’m busy fabricating the mirror-image metal parts for the other door and will probably postpone the actuator re-design while I test and evaluate the function of the first one.