Ok. I am working on drawing out a 3-story historical building. Right now, each floor is cut--so I have 3 separate floor plans. What I would like to do is to add a model space viewport? so that I can overlay all of the floor plans on top of each other. Theoretically, any changes made to the separate cut floor plans will reflect in the overlaid plan. Is this possible to do? This is simply to make it easier to view the interaction of beams and headers between floors.....and, again in theory, would make it much easier than overlaying the separate cuts after every change.

I don't see a way to use modelsapce viewports, or paperspace viewports for this.  They are just different views into the model, so couldn't be overlain effectively.
 
By "cut" do you mean separate details, not overlaid?
 
Could you not just have each floor on a separate layer, and have them overlain?  To work on one layer at a time you could "isolate" it (layiso command) to turn off all other layers.
 
Another approach, have each floor in a separate drawing, xref each into a master drawing for comparison.
 
and, did you have any luck with my suggestion for starting a drawing with the template open dialogue?

Carl-Thanks for the reply. Yah, I didnt think there would be a way to do this.Each "cut" is basically a section cut at each floor, like a floor plan you would see in Architectural plans. Everything from each floor is on its own layer, so yes i could just simply turn on/off layers as I work and now that I have each floor drawn out, that is probably the route i will take. In regards to the other post. Yes, I tried the script and got it to open with choosing the template, but I also got the same drawback of opening a drawing directly. So in the end I just created AutoCad shortcuts of the more commomly used templates and put them on the desktop.

Thanks for the feedback.
 
You might want to try modifying the AutoCAD startup icon properties (ridhtclick)
 
And under "target" add at the end the switch to run the script - rather than having acad.lsp run the script. Something like the following (use name of actual script file):
 
"C:\Program Files\AutoCAD 2008\acad.exe" \b "opentemplate"