Seeking Advice: Vary Paced Long/Easy Runs in Training - Yay or Nay?

My running training (Currently mostly 10k/21k races. Marathon planned in the future) is currently structured like this (50-60km a week):

Monday: Rest

Tuesday: Speedwork

Wednesday: Easy Run (10km+)

Thursday: Easy Run (10km+)

Friday: Rest

Saturday: Threshold

Sunday: Long Run (15-20km)

However, lately, I've been thinking about shaking things up a bit by incorporating varying paces into my easy runs and long runs. Specifically, I'm considering running 1-2 km at a faster or very fast pace during these sessions. The goal is to simulate race conditions and train my body to adapt to different paces.

For example a 10k easy would be 5k easy - 1k racing pace - 4k easy.

Here are some additional questions for the discussion:

How do you think incorporating varying paces into easy runs and long runs could complement a more classic training approach?

Have any of you mixed up your training routines similarly, and if so, what results have you seen?

Should there be any adjustments to the rest of the training week if you're incorporating varied pacing into easy and long runs?

Are there any potential risks or pitfalls to be aware of when incorporating faster segments into these specific runs?

I'm eager to gather insights from those who have experience with both classic and varied training approaches.