Revit 2016 added the ability for more complex, comma-separated revision sequences to deal with specific requirements. As part of this change you can also copy and paste your sequences into this field.
Quick tip - if you wanted to pre-populate an entire custom sequence, it might be easier to keep a text file and edit the list in another application.
Revit will do some basic reformatting of the data - for example if you copy and paste this:
Revit will reformat it into this after you click OK: