Is it possible to set up multiple sites in IIS with the same domains bound to them as long as only one is switched on at a time?
So yes, as you've said - they just can't be on at the same time. That is unless you assign each one a separate port. Then they can all run at the same time as you're forcing them to pick the correct site when you put the port in the URL.
If you're on XP, check out the tool IISAdmin.NET. It lets you host multiple domains (only one enabled at a time) and quickly lets you turn them on and off. You can't normally even have multiple sites in XP.
BTW, I'm not affiliated in any way - I've just used it (a lot!)