So... Written? No, but a plan? Sure!
1st, you want to KNOW there's a problem. That's why monitoring is so important, If temp varies, power fails, pump electrical draw changes, pH spikes... Apex alerts me. Knowing that you've got a problem, quickly, is critical.
Power outage: Running a small Tunze flow pump on a battery switch, it'll run for 24 hours or so, give me time to respond. We have a gas generator, it'll run the return pump and heater. Tank can do without all the extras for a while. Only real problem would be an extended outage during the summer... no AC would be an issue, but that sort of thing is quite rare. Generally, our power problems are during the winter storms.
Equipment failure: Once alerted, I've got a spare return pump, spare heater controller, and a spare heater tube. As long as those items are running, you've got time.
Tank/sump failure. 1st, try and minimize the risk. Quality gear is about all you can do. it's a Planet Aquarium tank, purchased new, in good condition. Sump is a BashSea, also purchased new, in good condition. Plumbing is all well built, strong, and easy to access. Stand is welded tube steel, way overbuilt for the load. Chances of a failure are as low as I can make them... but yeah. That's every marine hobbyists nightmare. I do have a 100g Rubbermaid trough in the garage. Ideal? No... but it'd allow me to re-home everything while I figure out what I'm doing.