I’m not a big fan of the Indian Industrial Complex (IIC) or the Sinkiang Industrial Complex (SIC) anyway. If you have the Colonial Garrison National Advantage that’s a different story. However, I’ve found those industrial complexes really draw more resources away to prevent them from falling easy than they give you in offensive power.
The S. Africa complex is a different story. I’ve used it often to great success in keeping Africa in British hands and later to shuttle tanks up to Caucasus and that pays itself back over the period of the game. (Also I have yet to lose a S. African Complex without costing the enemy great numbers of men and loss of use of expensive and powerful assets for many rounds. For instance, Japan once took out my Complex, but it cost them 4 fighters, 3 infantry in casualties and I tied up a bomber, 3 battleships, 2 carriers and 2 transports for three rounds. One to line up the attack, one to move to attack and one to move back. In my mind, it was worth the 15 IPC investment, especially since Japan was pushed out of China and Manchuria that same round.)
As for no infantry buys, my personal favorite is the 3 fighter or 2 bomber purchase on England 1. I have also done the 4 fighter purchase with germany, the transport, 2 submarine, aircraft carrier purchase on round 1 and the artillery, 2 fighter purchase on Russia 1.
All fun. ^_^ (Notice I said fun, not that I won any of those games. This is, after all, my year of off the wall strategies!)