No, I would not attack China, Saudi Arabia, and Russia all at the same time, very early in the war.
If the Russians enter Persia I would immediately Declare War on them to get the Persian Oil, unless the CW was very, very good at getting it themselves. Regardless of what turn it was.
Otherwise I would open against the ChiComms in the fall, push Chiang around in the winter, hit Mao again in the summer of '40, and then invade Saudi Arabia later in the summer when the 2-4 SNLF division is ready. An advance built Yamashita would arrive in September to give the Japanese a lot of options on the ground. It helps for Japan to scrap some early TRS to be sure to have the long range ones available in numbers.
Against good Russian play, I would not attack them until M/J 41 along with the opening of their war in Europe. Perhaps the same turn given a '42 Barbarossa, to suck them into Siberia. For a '42 question, a lot would depend on map positions that can not be postulated much in advance very well.
By the fall of '41 they might have 18-19 BP a turn cranking out, with gas for their units arriving by tracing to the Middle East, which will keep the IJN mobile somewhat for free, until sometime in 1942. Then it is easy to build the SYNTH plants. Early on, I'd rather have the extra units to go take resources with.
I don't feel the Japanese can play conservatively, building the SYNTH early, attacking only in China, to have the best chance of winning.
It is interesting to consider how many ports there are on the 2 China Seas. But you get them all simply by taking Singapore, Batavia, Hanoi, and Manila (perhaps Timor is neutral). Changing them to Japanese control is generally not the problem. Keeping the West out is. But some Allied play can certainly make it difficult / time-consuming to take them, and that's where you need all the Build Points you can get. Most Allies idiotically ship MacArthur back to the USA, as if the Americans can't afford 5 Build Points.
And I'm really not sure why the idea of building a Convoy Point in Persia was brought up. I have had the Germans or Italians do this in games. I guess it would be handy for a Japanese one to appear in a Persian port. But if the Russians conquer Persia, they can not build one, though I regularly have the Russians build 4 CP in the Caspian Sea.
If the Russians botch their attack on Teheran, Japanese assets can appear to make their second go more challenging. The Russians don't generally bring FTR cover into Persia with them …. but one bad throw of the dice, and they might find themselves needing it.