[x] Plan North: You're not confident in Schwarster's positions, and more importantly you're concerned by the fact he's only reported sporadic enemy contact. If you can work out a way to extend his supply area into the highlands proper, you can press the enemy dearly from a secure location in the massive highlands around the Great Lake.
[x] Get Schwarster to stick to small unit operations, and work on extending supply lines through road improvements or whatever means we have to improve the transportation network to the Great Lake, and then supply by sea or something until we can figure out land routes.
[x] See what he'd need to start running search and destroy operations, or at least burn us a big enough buffer that large enemy formations won't be able to live off the land.
It depends on if that factory is using all its capacity supporting the north.
As far as streamlining the south, whatever we can do to move central supply dumps towards the front would keep the logistics more responsive. If there's a way we can cut rough landing strips near forward supply areas, we could use air mail to more tightly match upcoming supplies to demand. Air cargo doesn't make much sense for anything bulk in this case, so that won't help the ammo situation.
Honestly, streamlining is likely a lost cause. Colonies don't end up on different standards because their units are considered
loyal. Especially not from recently acquired areas.
Go for Plan North. The South is full of defensible terrain and friendly locals. Giving them training, discipline and equipment will be enough to slow down invaders who don't know the terrain as well.
The real issue is finding some way to get our commander to get off his ass and let us press for fast strikes. A slow advance will have us suffer a logistical nightmare coming from being camped out in the bush rather than raiding and demoralizing opponents right in their home base. If need be how mobile can we get our artillery to be?
Honestly, infantry guns, modernish Field Guns and mortars should be pretty damn mobile if we can get them. As it is, Von Lettow-Vorbeck managed to haul 10.5cm SK L/40 Naval Guns all across German East Africa on a pretty quick timescale, so we should be able to do fine with equipment that doesn't weigh two tons. Especially if we can get artillery tractors worth a damn.