OK, About the 1/1, in post#4, yes, the bevels will lock, and will spin in 1/2 etc.giving a center RPM half way between the left and right input RPMs. (4,000 RPM on the left + 2,800 RPM on the Right = 6,800 RPM /2 = 3,400 RPM on the planet carrier (center sprocket.) Probably don't need 9 gears, but the in between gears (1/2, 2/3, 3/4, 4/5) might be useful as passing gears, and of course, the diff is a mismatch safety that a solid shaft with two in one out doesn't provide
In post #18, holding "B", or putting a load on "B" will simply cause the spur planets to spin as "A" and "C" are fed at an equal RPM, but different RPMs on "A" and"C" will cause "B" to turn at the DIFFERENCE between "A" and "C" (4,000 RPM on "A" - 2,800 RPM on "C" = 1,200 RPM on "B",) but again, inputs must be different. Only five useful gears, but a different spread pattern.
These things I was pretty sure of, but my original question had to do with the added power going through one side. I will address this next.