OK.
I've thought about it quite a bit. Think about the qualities it takes to be good at the 100 (or even an indoor 60, for that matter) and put that on a sliding continuum all the way to the qualities that it takes to be good at a marathon
The qualities on the sprint end of the spectrum are almost 100% neuromuscular while the marathon end is almost 100% aerobic development. As the OP stated, a higher sprint speed (aka better neuromuscular control) will translate to all submaximal paces being run at a lower percentage of overall top end speed. However, top sprint speed will never translate to longer distances without the athlete having spend years developing metabolic efficiency
IMO, the real trick to developing speed for ALL distance events is to be able to sneak in enough neuromuscular work without taking away from the athlete's ability to complete the training that will most directly lead to better metabolic efficiency.
There are a number of ways to do this:
The OP suggested dedicating a block of training to developing top end speed. Lydiard would do something like this with his athletes back in the day. However, looking at Lydiard's training. He never really worked pure speed. The closest his athletes came to doing pure speed work would have been during his hill bounding phase. But, the length of the bounds or hill sprints was fairly long and fairly high volume, if I understand Lydiard correctly, so his guys never REALLY did anything to develop top speed.
A number of coaches use things like 8 second hill sprints, or 6 second hill sprints once a week. It seems like most of the time, this is used during the fundamental period of training (aka, far away from competition). Hill sprints will closely mimic the neuromuscular requirements of sprinting, but not entirely.
I've seen other coaches have athletes finish their main session with some very fast running. (Think things like 150s where the athlete shifts gears so that the last 50m is near top speed).
With the exception of the hill sprints, none of those workouts are things that you'd probably catch a world class sprinter doing. This may be because, as HRE said, sprinters just don't want to do that type of stuff. I think a better reason that you wouldn't see sprinters doing these workouts is simply because you can never really hit top speed while you are fatigued. So, when sprinters want to hit top speed, they need to do it while they are fresh. AND, they do it knowing that for any given sprint session, they are really only going to hold top speed for a maximum of 3 seconds at a time.
The other thing to consider is that top end speed is REALLY hard to improve and actually improving top end speed takes years, not weeks. So, to answer the OP's question, NO. I don't think dedicating a random block to speed development and then forgetting about it for the rest of the training cycle is a good idea. IMO, here is the best idea. Touch on speed daily, in an non-exhausting manner. Here's a list of things you can do to develop your neuromuscular potential on a daily basis, without subtracting from your ability to train the energy systems that are needed for the 800 (or the marathon for that matter)
1. Drills - I'm not talking about the B.S. drills that you see kids doing at meets. I'm talking about focused sprint drills done in a way that will develop sprint mechanics
2. Accelerations - we do these 2-3 times per week. After we do a warm up jog and drills, we run 3 x 50m with each 50 a little faster than the one before. The last one is at top controllable speed. I tell the kids to build up throughout the entire 50 so that they are really only hitting their fastest speed for the last 10-15m or so. We do these before every race and every hard session (tempo, CV, VO2, whatever)
3. Alactic sprints. During our pre-season, one day a week will be dedicated to short sprints with full recovery. One of our alactic days will start as described above (but we usually take a warm up of 3-4 miles on these days), then the drills, then the accelerations, then we'll change into spikes and run races of 40-60m with a full recovery. I group the kids by ability level and the winner of each race has to start the next race 1m back. This gives everyone a better chance to win. Some days, instead of the races, will run timed 30m flies using our freelap system. Ideally, we'll see our fly times getting faster over the course of a training block, but that doesn't always happen. What I really want to see is that they aren't getting SLOWER.
4. Wickets. I'm a huge convert to wicket running. When we get into the season, we kind of run out of time for our alactic days. We keep working sprint mechanics using wickets. Youtube up a video of how to run wicket drills.
5. Agility ladders and BFS Dot Drills: We more or less stopped doing dot drills because they beat up the kids shins too much. Both ladders and dots are great for coordination, mobility, and balance. These are GENERAL ATHLETIC QUALITIES that usually go unattended in distance programs and often go unattended in sprint programs as well. I view general athleticism as the foundation for success in all sports and try to help my athletes develop athleticism. "Athlete First, Runner Second" is one of my coaching mantras (however, I keep that one mostly too myself, because most of my athletes would try to take that too far and end up neglecting the aerobic house)
6. Olympic lifts: look up some videos on how to do a power clean, a high pull, or a power snatch. We try to do Olympic lifts 2x per week. One day goes with our alactic speed day and the other day goes wherever we can fit it in.