That's very arbitrary.
The sun is at the highest when the sun is at the highest. It's called the solar noon. If you are in Thunder Bay, it happens arouns 1PM EST/2PM EDT. If you are in Gaspé, it happens around 11:20 EST/12:20 EDT.
See how much binding the timezone to a specific shift doesn't make sense based on your arbitrary metric?
Eliminating time zones would be pretty amazing.
If we eliminated DST for the summer, or would not have permanent DST, we'd need to change culture to not have 9-5 banking/office work days but rather 8-4, 7-3 or 6-2, similar to how the trades already work.