If I may ask, why would you want to structure your servers this way? With mojoPortal, you could be developing as many pages as you like, with the settings set to "hide from anonymous users", and update the settings to make the pages visible when you're ready to roll out the changes.
I know that Joe strongly recommends not attempting to migrate data from a secondary environment to your production web site; it should always go the other way, and this is what my professional database experience has borne out as well. Trying to merge databases will be a very difficult exercise, and not likely to work out the way you want it to.
At our site, we have have configured two separate web servers. One will be the production web server, and the other a development/test bed. We will periodically refresh the database on the development server from production, and use development to do training, "what-if" modeling, custom feature development, upgrade testing, etc. Any data that is to be included on the production web site will need to be entered directly into production by our authorized personnel.