1/ We have full visibility on base defense missions for example, so even if it's hardcoded (I don't know), we can easily extract it to ruleset.
In the terrain definition you can define a property 'revealedFloors' (going by memory, maybe the name is a little different) that makes the floor, for the map module in which it is defined, visibile.
(the alien base map module where x-com units are spawned use this, so check the alien base terrain for an example).
So you could just define a terrain with all its map modules having revealedFloors, with the result of making the generated map fully visibile.
Haven't tested but should work.