I do plan on experimenting with a technique that should work. Muxman allows you to do a sort of poorman's seamless branching, as long as the alternate scene is exactly the same length as the original. Basically, you make the replaceable scene a cell, and have the IFO playlist point to a different cell when it gets there. I was going to use it for the narrative segments in other languages (the subtitles will be selectable). Assigning different angles should allow the different language threads.

I'm not sure if there is any method to do true seamless branching at home.