Campaign Creations

I wouldn't bet anything on custom content seeing even remotely comparable freedom to what Brood War has. Notwithstanding actual file structure and executable changes, Blizzard has been hellbent on killing custom content since the beta of sc2. Their business plan is to introduce micro transactions into remastered as part of their no-commitment cash grab scheme, and modding/campaigns are their single greatest barrier for that. That said, they aren't even aware that Brood War had campaigns or mods, and no one remaining in their company is educated in Starcraft, so they might simply forget to do anything about it, too.

The other question is if Blizzard will allow their nice new high poly HD models to be dragged out of the game files since it will likely not be in .mpqs anymore.

People have already started decompiling the graphics so hopefully it continues.

There are no models, there are sprites, and they are dds and have already been ripped from the game (which uses CASC now).