I'm not sure how changeable the current architecture is, because SONAR emulates a traditional studio environment. The original idea was that the ProChannel would let users create a custom mixer architecture with channel strips that had interchangeable modules. The FX Rack was intended to be more like the rack processors in studios (e.g., rack mount effects and such).
If it could be changed, I think Kamikaze's idea of strips and flyouts probably would make the most sense
if you could "tear off" the flyouts and place them anywhere on the screen. Then if you didn't want to use FX Racks, you could just eliminate seeing them. This would also preserve compatibility with older projects that used the FX Rack. But if you want to keep having the bifurcated approach, you could do that as well.