I don't intend to follow the plan given, this was just an example of the idea I have been thinking about.
But you raise an important point about the highlighted sessions actually being quite difficult on the easy days.
So how about instead of halfing the sessions, reduce the pace whilst maintaining volume. But the pace will still be more specific to 1500m running than 7:00 min+ miles. You can take as much rest as required between the reps, idea is to run relaxed and finish feeling fresh.
Reviewed example of potential easy sessions:
6 x 1 mile @ half marathon pace
5 x 1km @ 10k pace
8 x 600m @ 10k pace
6 x 400m @ 5k pace