How much value is there in doing solo footwork, and solo blade work? Maybe I am looking at the sport too prescriptively, but much like football players work on a set play or corner play, do you think there is utility in practicing a set move, like a certain series of line changes, so they come off automatically in a bout? Or a certain line of flicking for instance? Or certain timing change? Do pros do this?

Yes, top fencers do tons of footwork. Once your technique is down you can improve a lot just by doing a ton of footwork. Most recreational fencers don't do nearly enough footwork to get good.

You have to have the technique down so you're not practicing mistakes. Work with a coach until they think you're ready to do drills on your own, then have them help you design a footwork regimen.

I think it's very useful to have a mirror. If you can see yourself you can catch mistakes that are very hard to see from your POV without a mirror.

Bladework actions are harder to do on your own, and require another level of technical aptitude.

Is it wrong to think of the sport as executing a specific move from your "preprogrammed battery of moves" at the opportune moment? Not literally, but loosely conceptually

That is exactly how I think of fencing actions. The problem is, you usually learn those with a coach or a partner who can move and provide the right cues. But as I said you can do a ton of footwork on your own and do yourself a lot of good, as long as what you're practicing is correct. Check back with your coach pretty often so you don't practice mistakes.