I run between three different systems just about every day, each has different plugins and versions of Pro Tools. Here are a few ideas from my own experiences.
1) Buy extra plugins for another system. Too expensive, I wouldn't bother.
2) If you want to keep your effects you can export them(individually) from your Primary DAW and they will retain the effects from the plugins. Then move them to the new system. This also helps to build your own library.
3) Internal Laybacks for each track and export. You'll have your dialog, music, and effects on separate tracks, but editing them in great detail will be rather difficult.
4) This will sound insane, but it works. Use only the basic plugins that each system has. Just about every sound designer I know would probably shoot me if they read that.
5) Do as much as you can from one system. If you have multiple individuals working on separate computers I would delegate a specific job to each one. Dialog for John Doe, Sound Effects for George, music for Yoda and final mix for the man with all the plugins. This keeps you from having to worry about which Mac/PC has the right plugins as they would bounce out their own track.
Hope that was some help, bedtime.