The only reason people don't want cross server battlefield is because no one wants to be paired with super OP opponents.
As long as the do the battlefield in tiers (only put players within a specific range of power together), cross server wouldn't be a problem for anyone I'm sure.
Personally, I would like a cross server Ranked tab. You know, so they don't get rid of the 2 tabs we already have, but also have a tab for cross server