Deadlines are global because communal dates are Good for niche games like Ottoneu. There is already a ton of fracture between 4 scoring systems, H2H points, and playoffs. Ottoneu is a very small community, and having shared dates creates a sense of commonality between the 400-odd leagues.
I don’t think it is early. It is tied to making commitments to your league for the upcoming season, which is a natural combination. Managers should make this commitment both in terms of setting your keepers and paying for their team early enough that if they choose to bail out, there is time for them to be replaced.
If you want to do post-draft stuff, you can consider drafting earlier!