In line with the Research-quality issues posted in another thread, I came to think about... the oddity that it cost absolutely nothing to totally alter an industry's production..
Take a Steelwork
After a certain research level, it has several options of production..
Steel, Copper Wire, Aluminium, Highgrade Steel
Well, if you initially start a production of Steel, then you purchase 1 type of equipment for that. But I am 100% sure that the same equipment would never do as Aluminium production equipment..
So perhaps implementing a cost of change on productionlines (production initializations) would be a good idea?
(First time you initialize a production, it could either be free, or cost something, maybe lower cost than second-change - depending on what the goal is for you developers)
Just a thought for another money-sink, which is so badly needed in this simulator :]