Hi and welcome to the site.
I also want to avoid getting injured at the age of 65.
Sounds like a good plan. I want to avoid getting injured at the age of 42 so we are of similar mind
Presently, I am confused about the role of the Central Nervous System for improved exercise performance
As stated that is an academic question. That is, depending on whatever performance skill you are looking to improve, there will be central nervous system changes that are part of that adaptation. But you train with sound means to improve performance not to worry about what your CNS is doing. It's kind of like wondering how you breath. While you're thinking about it you suddenly realize you've been holding your breath.
That said I went into some of the CNS roles in strength development in the "Strength versus Bodybuilding' eBook and feel free to start a thread about all that.
and how to incorporate routines that use all three energy systems (assuming this is a good idea)
You mean the phosphagen, glycolytic, and oxidative systems? You are always using all three to some extent or another but one is at the forefront depending on the relative intensity of the exercise.
If you want to break it down easy you'd say that if your doing resistance training which is primarily anaerobic, you always use the phosphagen system primarily for the first few seconds and then rely on either fast or shifts to slow glycolysis depending on the time frame of the exercise.
However you could say look at it also in terms of say, very heavy lifting versus marathon running. Lifting a near maximal weight once relies almost exclusively on the phosphagen. That is very high intensity very short duration. Running a long marathon relies on the oxidative system. That is very low intensity very long duration. So that is your two extremes.
Now say you lower the weight on that lift and start performing more reps. This is still a relatively high intensity acitivity. So you rely, for the first few seconds on the phosphagen system and then a shift to fast glycolysis. Then if you continue on, increasing the duration, which means lowering the intensity, that shifts to slow glycoloysis and on to the oxidative system. Keep in mind that there is never a well defined cut-off between them. Just one is always at the forefront depending on the intensity and duration of the exercise. But never does ONLY one energy system supply all the energy. This is something that people don't usuall get.
You don't need to train "energy systems" you need to train to increase performance in the areas you want to. The appropriate metabolic adaptation will come along for the ride. Trying to train all the energy systems is really saying you are training to maximize both aerobic and anaerobic capacity. And you cannot do that. Yes you can train to realize better performance in both areas but you can only be "really" good at one of them. This is really about specificity that it is energy system training.