I'm assuming the OP means something like Skyrim open world, or at least the Zelda Ocarina of Time - Hyrule Field ways.
This game is already open enough for me, and I really want valleys and some restrictions in some places like I think some are wanting. I think this game offers that, though, I have not seen doors, caves, interior structures, etc. in the Jungle level yet, which is a huge suggestion I would love to put out.
Then again, this is still early in development.
But I can already see some restrictions so far I think.
As for the big fields like Skyrim or Hyrule Field again, I wouldn't mind a special level being in that form as it is. xD