Interesting problem.
I'd probably look at the other rear door to see if it might be possible to bend a tool of some sort to toggle the child safety switch when the door is closed. Or, take the inside trim panel off the other door and see what the mechanism is, figure out away to reach something in between the window and the door to snag whatever the handle pulls
I’ve replaced probably twenty door handles on my vibes over the years
I hadn't noticed door handles being a common Vibe problem, any idea why you've had so much trouble with them?