3
I'm not so sure.
What seems to be required here is a combination of 3 elements:
1 - Customised menu: Multimenu will do nicely
2 - URL re-writing? This has been covered in a few topics recently, and apparently should be possible with XOOPS 2.3
3 - Different layout on different sections: You need a theme switching module, and some variations on a standard theme designing.
Most of this should be possible