ORIGINAL: obvert
You also can't be 'armor heavy' this early as Japan. Your tank divisions aren't complete in the beginning and you have to plan to make sure those units are in the same places when the other parts arrive through the first several months of 42 so you can buy them out and bring them to China. So the schedule is off for this reason alone. I'm 'getting the timeframe' and it doesn't work.
I like thought experiments.
IJA tank units as of Dec 7th 1941 - NB: this is a hastily prepared list and may not be absolutely accurate.
We'll ignore the Recon Rgt's, seeing as they combine to form divisions and can be quite handy.
You've two tank regiments in Indochina that can rail up to SW China within a week.
Two tank regiments on Pesacordes and one on Formosa are ready to be sent to China on Dec 7th.
One tank regiment is already loaded on a TF at Samah.
That's six tank regiments ready to be in South-West China by Dec 10th. Roughly two divisions worth.
There are 7 tank regiments in Manchuria, about 4 of which can be bought out on Dec 7th (assuming the inital budget of 500 PP's is spent) and the remaining 3 can be bought out at a rate of about 1 regiment every two days.
On top of that, there are two tank regiments and two armoured car units in Centarl China that can be bought out and shipped to South-West China.
At by the end of December '41, you can have 15 tank regiments and 2 armoured car units deployed in South-Western China, assuming you prioritize PP's towards buying these tank units out.
The impact on the DEI effort shouldn't be noticable. You'd still be keeping the detached Recon Regiments, so you'll still have mobile units that can take weakly held bases quickly. In exchange, you'll be able to have the bulk of Panzerarmee China en-route towards Liuchow/Kweilin by mid December '41 and nearly all of your armour concentrated by January '42.
IJA Paratrooper Units and targets
Units
Yokosuka 1st & 3rd SNLF - Kagi - 24 AV each
1st Raiding Regiment - Kagoshima - 30 AV
Targets
Tuyun - defended by 3 units (30 EXP/Morale) - 96 AV
Kweilin - defended by 1 base force - 28 AV
Kukong - defended by 3 units - 28 AV
Execution
Kweilin and Kuking can be attacked by paratroopers on Dec 7th by the Japanese. With heavy use of bombers from Canton and other bases in South China, there is a good chance of success. This isolates South-West China from the bulk of Chinese troops around Changsha.
Tuyun is a bit more problematic. The 1st Raiding Regiment can be moved to Amoy around Dev 11th/12 by fast transport (plenty of CL/DD heading that way from Japan anyways), so with a bit of effort, you can have all three IJA paratrooper units attacking Tuyun by mid-Dec '41.
One Tuyun falls, the Chinese can't rail troops to set up the roadblocks and the Japanese can fly in troops of their own to keep South-West China isolated.
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