Edit: it is different if you adopt an elderly isolated cat that would otherwise be put down. In that situation, you'll still be providing them with a life, but if you do get through to them, they will bond to you, and it will still make leaving for trips difficult, even if they're used to your daily absence. A support network is inherently more flexible and robust then a support pair.

The fact that you're putting this much thought and consideration into it, signals that you would probably be a very good cat owner, and I don't think you should write the idea off.

Just, try and find a cat that seems independent, and 6 months or a year in, look back and reconsider if it would actually be that much harder to add a friend to the mix.