Tu_79, I agree with several points you've made, but overall I still think that for a non-warmonger, industry's happiness bonuses aren't that crucial compared to rationalism's. Rationalism decreases unhappiness from religious divisions, boredom and illiteracy (and also slightly poverty, I think, due to specialists gaining +1 gold). Furthermore, if you've managed to found a religion (which ought to be a very important goal for any non-warmonger), you can often get churches (which are paramount in spreading your faith) and pacifism (not only gives you happiness, but decreases costs of missionaries, further helping spreading and increasing happiness), and I've almost never seen the AI pick the "One world, one religion" reformation belief (where missionaries act like mini-prophets). With a combo of pacifism&one world, one religion, it's very easy to spread religion to the 4 AIs that haven't founded (and which will never be angry at you for spreading your religion to them) and thus gain a lot of happiness. Lots of happiness means that you can afford to sell more luxuries (giving you more money), that you can ignore building some buildings that you would otherwise build to reduce unhappiness (thus saving you money/production), work more specialists etc. Extra growth can be a big boon if you're friends with 2 or 3 maritime city states or if you pick Mandirs or the food follower belief (or if you haven't founded a religion, if a religion has spread to you with Mandirs/food follower belief).
Churches are imho OP. Pacifism seems one of the best enhancers for a non-warmonger (1 happiness imho is worth much more than 1c/1s or 1g/1f per followers, especially in the later game, and it helps you spread more than the enhancers helping with the passive spread). One world, one religion is uber-strong for spreading your religion (and another bonus is that it doesn't really benefit the AI you've spread your religion to, whereas other reformations can turn out to benefit the AI more than you as the founder). If you manage to get pacifism + one world, one religion (and the AI very rarely takes either of them), you'll be having lots of happiness, and if you get churches, it will be even better. And that removes a huge reason for taking industry as opposed to rationalism.
Again, that's just my opinion, but when I'm playing a non-warmonger game where I'm a founder, I see little reason to go with industry instead of rationalism.