Imagine if humanity realized that collapse was coming and wanted to do something about it. What, if anything, might work? Here is my suggestion.
Step 1: Admit that we have a problem with collapse! (Read Our Finite World.)
Step 2: Form a world government. Declare a summit, form a world alliance and neutralize all resistance immediately. If any major nuclear powers resist, our civilization will probably end right here, but let's assume they understood the gravity of collapse and went along. Perhaps not all minor countries need to participate -- the rest can be left to their own devices as long as they don't threaten anti-collapse efforts.
Step 3: With intertribal warfare ended, humanity shall declare war on collapse. Realize that collapse is more formidable and destructive than any other foe, so we need to set aside our cultural differences. What we are facing is just as bad as if an asteroid were on a collision course.
Step 4: Conscript people to fight in the anti-collapse army. For example, conscript Gail Tverberg as chief systems theorist and Keith Henson as chief engineer.
Step 5: Anti-collapse forces should control a minimum of all needed ingredients to have an industrial civilization, using violence to enforce operation (but preferably not more than needed). The goal is to allow the system to scale down without losing maximum complexity, so smart people need to figure out what we absolutely need to preserve and leave the rest alone.
Step 6: Free trade can still exist, but the anti-collapse army must be able to commandeer all resources as needed in order to preserve complexity. Pick some companies more or less randomly in every industry and see to it that they don't fail, and do the same throughout their entire supply lines. The entire oil industry might as well be nationalized immediately since it will never be profitable again anyway. Countries can also keep their laws and customs as long as they don't interfere with the war on collapse.
Step 7: Adopt more sustainable practices going forward. We need to lower our expectations and tolerate the fact that there will be many losers who will perish. Perhaps only soldiers in the anti-collapse army will have adequate nutrition and a good quality of life, but that's OK as long as we maintain maximum complexity. Stop population growth! All while keeping technological progress or at least not losing our ability to manufacture any amenity that we have now, the preservation of which is the whole point of the war effort to begin with. Nothing lasts forever, but if collapse is delayed beyond our lifetime, consider this plan successful.
There is no single dictator who can make this plan happen. It doesn't need happen democratically either, but a lot of important people need to understand collapse and desire to do something about it to put the plan in motion. It is a truism in doomer circles that our economy must grow or die, but I wonder if that is really true if something like this plan were implemented. It might be impossible for social reasons, but I can't see any thermodynamic reasons for why it can't work.
One might object that this will be some horrible dystopia comparable to the worst communist regimes in history, but I have my doubts. If collapse is really imminent due to resource depletion, there won't be enough resources to oppress people for frivolous reasons, so the only way industrial civilization can live on is if it is concerned with self-preservation rather than insane and wasteful projects of oppression. Having a police state micro-manage people's behavior complete with mass incarceration will be beyond the power of our civilization going forward. There will be exceptions, but I think most people would simply be left to fend for themselves or starve rather than be oppressed by the state, and that is no worse than what would happen during collapse anyway. The question is only if we want to use our remaining resources to preserve our technological capabilities and a good life for at least some people instead of letting collapse happen without a fight.