There is an end to this story. I wrote my own finger-friendly Qt implementation of Maemo5's native contact chooser. As far as I can tell, no Maemo5 developer ever used the native one in the way I want to use it. I'll go so far as to say that the native one is broken.
Writing my own was harder than I expected but not impossible. I had some help from some Trolls at Qt Developer Days in San Francisco. I'm grateful for their eager, friendly help. Thanks to Martin, Benedikte, and Pierre.