I think they are all excellent suggestions. The Mr. Moto film would be a particularly interesting entree. A curiosity, a look at what might have been. Of course, I don't have any of his films and have not seen them in many years. I hesitate to buy them worried they would just collect dust on a shelf. (no such worries with the estimable Lt. Chan) While I like them , I don’t love them enough to spend the $40 plus dollars for the set. It might be interesting to screen a few of them and compare them to the Chan series. Then there’s the Mr. Wong films. I don’t believe I’ve ever seen the one with Keye Luke.
I understand your feelings about purchasing films that may "collect dust." However, I did see both Mr. Moto sets at Costco selling for, I believe, $31.99 each just last week, if this helps.
The Mr. Wong films are great. The one with Luke as Mr. Wong is a bit of a stretch after having seen the others, but well done & fun to watch. I especially like the scenes with Lee Tong Fu fussing about.