That "can spend 1 morale for 20% progress" sounds like something that could lead to some real bad stuff if abused, but so could massive corporations, so we should probably try to balance the two. I'm not quite sure how we should make sure the viable requirement for interest-free loans is judged fairly, but I'm thinking a low general standard of just 'is this plausibly profitable' and a cap on loan size to discourage abusing them. Balancing the taxes so we don't lose any total tax income should be easy enough, though the ratio will need to be regularly updated based on market trends. Probably less practical than the other options but will hopefully mean better conditions.
Not sure, but maybe the boni could be something like this?
-5% Progress cost to all Industry Actions, remove money cost/per turn, can exchange material cost with monetary expenses. +1 Morale to all finished Industrial Actions, +1 People cost per Industrial Action/Stage