It's my feeling that for the South it's too easy to economically survive in the long run. In not one of my games the South got stressed - even more - in some of my Confederate games its seems I'm outproducing the Union on ironclads.
I think the one thing missing is the fact that the southern economy was very inflexible.
As soon as blockades were becoming more effective - one could notice that the stocks of cotton were growing in the Southern ports - and prices did rise even further. For each bale of cotton rotting in port - no goods were "traded" back into the CSA.
I don't think that plantation owners switched to agricultural goods like crops, weat and potatoes to feed the CSA armies. In fact with rising prices - would you jeopardise your business and turn it all upside down to start making goods like potatoes that probably would not never make nice profits. And accepting your plantations to switch over would both be sign of Southern defeat and be in total contradiction with one of the reasons the war was started - the difference in economical background between North and South. I think for each plantation switching over to food production the turmoil and unrest would rise.
Also I believe that Southern railroad connections were not dimensioned at hosting large scaled transfers of any kind of goods to the front states. By this I mean either food supplies, or any kind of supplies. Again the "switch" from a trading nation to a blockaded nation is quite a strain on even the local economies. The whole supply chain is dismantled and becomes overloaded with each port being added to the list of effectively blockaded ports. I think priorities in the goods needed made it pretty hard to have a sound logistical system.
Another remark is about the war supply production upgrades. If you are lucky you can get a whole series of war supply upgrades without investing
extra money in the industry. I mean - I recall games where I had about 4 successfull war supply upgrades in 6 months time. This is huge compared to the fact that the upgrades will pay back rather quickly ... and during the first war year you can spare such investments as the battles are still limited and the AI can be kept at bay pretty easy by your CSA.
So summarised =
1. For each upgrade on general supply production, a NM point should be deducted. See my motivation above.
2. Blockading should also reduce Southern transportation capacity - and Southern supply effectiveness- as more and more goods are needed to be stuffed in the already overloaded Having many engines is just nice - but if you lack the rail capacity - or the system gets overloaded - it won't be possible to manage all things.
3. Succesfull upgrades on war supplies should deduct a figure of war supplies from your war supplies pool. This is to reflect that upgrades on war supplies are costing many many investments of other "heavy goods". Please notice that the cost for industrialisation is payed nevertheless - in disregard with the fact wether or not you upgrade was succesfull. If you have a succesfull upgrade, you will lose some war supplies extra. This is too prevent "hoarding" on war supplies if you are lucky during your first months of the game.
I believe these things will improve the game further and are not that difficulty to implement. But my general impression is that industrialisation for the South is too easy.