Here is some concept i have for the interface: (click onto the picture to make it larger)
some explanations:
-The current pack file field works like a browser where you can select files to add them to the Entities via drag and drop (this is more comfortable than always type in all the names of the files) Underneath this browser(in the same field) will be a button 'add file(s)' to add files to the pack file.
-The Misc field is there to support this browser-type selection field: it shows the contents of the current folder in the pack file in the 'miniature'-view of windows explorer. This way you can see how textures look, and you can easily distinguish sound files from actor files or bitmaps. It also works with drag and drop and is often used because of its advantages. (I know i have written something else on the picture, but that idea just came into my mind)
-The File Preview Field is there to show actor files. You drag them into it and then they are rendered in there. You could also
drag sound files onto it and then a mini-media-player appears (with just 'Play' and 'Stop') so that you can hear the sound files before adding them.
-The Brush/Enitity-field changes to 'Brush-Field' when 'B' (for brush) is pressed and changes to 'Entity-Field' when 'E' (for entity) is pressed.
-You will switch on/off Navigation mode with pressing 'C' (for camera mode) in Navigation mode you cannot add Entities or brushes other than some exeptions (like lights (with L), spotlights (with S), or pawns (with P)). This is because in Navigation mode you cannot get the mouse from the center of the view (because of the FPS camera). However, Entities can be selected and also deleted. Here the edtior can show his full strenghts as you can add Entities quickly, then move around to look how they look, if you don't like the scenery select and delete them and then add them again. You can get out of Navigation mode with pressing 'C' again. Then it becomes more easily to edit brushes for example. Editing of brushes will work somehow like Truespace.
-In Navigation mode, there is no gravity for you, but collsion detection is on (for now, so that you can get a feel of how the game will 'feel' for the player, i may implement a feature to switch it on/off, but i somehow like it better this way)
-Entities will by default be added at your current position and with your current rotations. This way it gets faster to add Entities, because you know what the Entitiy is 'seeing' (usefull for spotlights, for example, also good for enemies, you know when they can see the player and so on...)
-There will be feature that allows you to drop things to the floor when you have selected them (used with 'D'). This is good for all actors that stand on the floor, maybe you have asword lying there and you don't want to adjust it's height manually you just press 'D' and it's done automatically.
Most of those thinghs are just concept, but i could make this editor as soon as RF2 is finished...or as soon as i have the libraries of RF2 (to Andy: it would be good if you would compile the RF2 source code as a lib (i don't expect you to do a dll as this would be more work) together with an include file, you don't have to do this, but it would be nice to have it at the end so we can access RF2s functions for writing tools for RF2)
The only thing i have no clue about is the 'browser' thing, but until RF2 is finished i can easily learn that.
Anyways, what do you think? For me, this is the dream of a game editor.
I will be away for some days and would be glad if there were some replies when i come back.
BTW, the models in the picture are just debug models which i build to test the 'feel' of the editor.
But i might still use it on this project by then since ill then probs use it too improve the levels ive made in RFeditpro. 
It was intended for putting together quick techdemos, not as the final (or even a publicly released) editor. RFEditPro will replace it as an interim editor for RF2 until the new editor is made. Here is a screenshot of it:
