To preface, I'm going to reference Unreal a few more times only because that is what I'm used to. I'm sorry!
Honestly I don't think having multiple 3d planes is /that/ useful. You really only need one. Retaining the option to set ANY pane to a 3d perspective would be nice, but most of your work should be done in just ONE 3d plane in order to make the workflow more efficient - by allowing you to access 2d planes as well.
I googled a bunch of level editors to make sure I'm not crazy because I didn't want to just reference unreal again because that's what I'm familiar with. I looked up quake, unreal, counterstrike, and doom. You will notice a trend with all 4. - They all have a 2d wireframe workspace so you can align objects perfectly without having to rely on 3d.
There is usually 1 3d workspace and 3 2d workspaces. See the attached pics
IIRC in the unreal editor you still have the option to change ANY of the 4 planes to any perspective you want. You can have 4 3d planes, or 1 3d plane, 1 top down 2d, 1 side view 2d, all panes 2d, etc. Most people work with 1 3d pane and the rest 2d.
Also - I downloaded the new firefly and had a bit of trouble moving objects about. Its a bit confusing to me IMO. I feel like there are far too many actions in order to move objects around sometimes.
Here is how unreal handles some of it.
and an article that shows all mouse controls in detail.
The user can make a multitude of movements without ever having to move his/her mouse to select a different point. The option to move vertically, horizontally, or forward and back AND rotate are all at the users fingertips resulting in an extremely easy to grasp, efficient control scheme.
I'm not trying to say MAKE UNREAL EDITOR, but I do believe it, along with other 3d editors that have been around for ages were designed a particular way for a reason.
Thanks for the response and I hope that this is helpful at least to some degree!