Sounds quite good. Brilliant, in fact - it perfectly handles the problem of wasted space by eliminating what isn't needed depending whether you are solo / partied / raiding. I think it'll work great.
Rather intelligent too, I think, is the adjustable raid frame idea. You might want to take a look a PRaid (PerfectRaid) for some ideas with regard to easily configurable raid frames. The layouts wouldn't be right, but those raid frames are effective with regard to how they handle displaying a large amount of information in a small area without looking "messy" like some raid frames such as Grid.
The loss or shrinkage of the minimap might be a bit of an issue, but, honestly - Have you considered ignoring the minimap and letting it live up in the top right corner? WAIT!
Before you dismiss the idea - Here's why you might want to think about it. I am confident that others, like myself, do not look at the minimap when we are engaged in combat. It's not useful. It's like a tachometer on a car with an automatic transmission. You don't need to look at it. So - Why not get it out of the way, so you can have more space for your important, combat-centric information?
Think about it.