The DM map editor will support "Editor Definition Format" files, XML documents that allow gamemode scripters to define the basic elements and settings required for a map to be compatible with their mode. So, mappers will be able to create maps with no scripting knowledge, provided the author has created one of these files.
In particular,
Pickups are considered a basic type that will be available on any kind of map.
They are supported as standard map settings, so yes.
This could be specified as a gamemode setting by the gamemode author.
Again, these can all be specified in the EDF file.
All of these, however, you would need to script yourself, unless the author provides this degree of map customizability. But it's most likely that no one will, as it is way easier to implement these in a script file packed in the same resource as the map, which contains map-specific code.