I have a PM that is built to run daily at 1pm. I now have a requirement to have

This can be done. But not in 1 PM. My method will require 3 PM.
1. - Which will have actual nodes to execute (without any timer on start event).
2. - A PM with timer on start event scheduled for 1300 hrs (Use PM 1 as subprocess)
3. - PM with timer on start event scheduled for 1700 hrs (Use PM 1 as subprocess)

This way you have your code base at one place and executed multiple times. Any change in business can be achieved by doing changes in PM 1.

This can be done. But not in 1 PM. My method will require 3 PM.
1. - Which will have actual nodes to execute (without any timer on start event).
2. - A PM with timer on start event scheduled for 1300 hrs (Use PM 1 as subprocess)
3. - PM with timer on start event scheduled for 1700 hrs (Use PM 1 as subprocess)

This way you have your code base at one place and executed multiple times. Any change in business can be achieved by doing changes in PM 1.