The "workshop page" will be that deviantart group Marios-sandbox.deviantart.com just create a deviantart account and upload your creationg when you have tested the upcoming devolopment kit I'm working on.
About the game editior, it will be divided in the following sections:
-Map editor: Where you create all the static things that your level will have like walls, floors, buildings, etc...
The map entities are composed by 3 kinds of contents: the floors and roofs, the walls and the navigation mesh (It is a key component for the NPC's AI) You will be able to create your own 3D models for the map.
-Weapon editor: There will be 2 kind of weapon editors, the "Player wapons" and the "NPC weapons" where you will be able to import your own gun models and modify properties: like the damage, the firerate, etc...
-NPC creator: Well the NPC will work 2 diferent animations the "static" and the "dynamic" in other words, when they don't walk and when they walk, obiously you will be able to replace the NPC 3D model and edit their animations and behabiour.
-Prop editor: This is the most simple of the editors, just create a 3D model, copy and paste it into the game and copy the behabiour of another existing prop to your model and you will be able to manipulate that object in the game.
That's all from now, tell me if you have any questions or sugestions please.