Rush,
It could form an interesting triptych of tales. One set in the twenties or early thirties in which they work together as detectives. One set in the late thirties early forties in which they are government agents working against each other. The final tale set in post war Tokyo working together again but with some animosity over the invasion of China or perhaps there could be an explanation of why Jimmy Chan and Mrs Chan stopped being mentioned in the late forties.

As for James Lee Wong, oh the possibilities are endless. In the first film it is made clear by a former acquaintance that Wong changing his name would not be unexpected, and as you note Wong vanishes once hostilities with Japan start. It would be fun to explore two possibilities (1) Wong's elimination by Moto, or perhaps investigated by Chan, or (2) Wong as a japanese born ethnic chinese (a surpressed minority fiercely trying to prove their loyalty) working as an agent for the Japanese who then goes underground when hostilities begin. And what is his relationship to the other Mr Wong (based o Keeler's Sing Sing Nights andnplayed by Lugosi in Mysterious Mr. Wong). Note that William Nigh directed both Lugosi and Karloff as the two different Wongs.

this is a very interesting speculation topic.

For me, I would have liked the idea of seeing Charlie Chan meet up with famous attorney "Perry Mason" on one of the Perry Mason shows. Perry Mason first started in 1957 so the Chan who would have met up with him would have been Roland Winters (if the series carried on). Imagine Sen Yung working with Paul Drake on some detective work. It would have been interesting to see "pop" conversing with Perry on crime scene details. An interesting show it would have been.