The thing people usually ignore is sprint development.
(I know you say distance runners never sprint at anytime during a 5K, however you are dead wrong. They should be able to sprint at the end IF they paced it correctly. Classic running form should always be worked on.)
Do not get me wrong, I come from the groups who wanted to do lots and lots of hard interval training.
A good 10 day microcycle would include all of the elements of training.
Doing MULTIPLE speeds prevents injuries as well as improving overall speed!
Sunday: Long run (Starting with your longest and every two weeks adding a mile to it. 9 miles is not too far for a 5K runner!)
Tuesday: Recovery run (Start at 1 mile go to 6 miles at a relaxed pace)
Wednesday: Sprint Training
1 mile jog, dynamic running drills, 4 x 60 strides; 5 X 70 @ 80%, 85%, 90%, 95%, and 99%. (Later 5 X 70 or 6 X 80) This is an important day. Do not follow it with a tempo run!
Thursday: Recovery run similar to Tuesday
Friday: Fartlek run starting at 2 miles going to 5 miles. Vary the length of the hard run between 2 to 5 minutes with shorter jog interval between.
Saturday: Recovery run
Sunday: Progressive run of 4-6 miles
For a 30 minute 5k runner this might mean 11 minute mile, 10:50 mile, 10:40 mile, 10:30 mile for the 4 mile run. You will want to beat those times nearly every week.
Monday: Recovery Run or Tempo run if feeling very fresh.
Tuesday: Hill workout. One way might be to take a slightly steep hill and
run 3 X 800 with a jog down to equal 6 miles. Maybe a tough hilly 6 mile run might be found instead.
Wednesday: 6 x broken 300s (First 100 at 800 pace, second 100 at 400 pace, last 100 close to top speed.) This is acceleration practice. You can also do flying 30s every straightaway on the track.
*You will want to warmup each day by either running slowly on distance days or on "workout" days jogging a mile, doing dynamic running drills and strides.
**It might be a good practice to finish recovery days with some short strides.
Underworking is always better than overworking. Most people over train.
Some may need more recovery runs.
***Eventually start adding one interval workout per week of say
3 X Mile at date pace (not goal pace for the 5K)
The mile repeats will be your key workout to prepare for the 5K but you need to put in lots of miles before you can profit much for it.
****Everything should get faster over time, however recovery runs need to be for recovery. Do not attempt to always run them faster. The long run does not always have to be getting faster either.
*****I am aware that this is not a complete schedule. You should have a year-round plan. There will be periods when you run three interval workouts per microcycle. Build up to that.