Why not use the XBMC skinning engine? I think they have a much more powerfull skin engine..
You know that MediaPortal skinning engine is based on a port of some real old XBMC skinning engine? Unfortunately it would require a huge amount of work to port the current version (porting something from C++ to C# and at the same time from OpenGL to DirectX is a big task especially when the skin engine is a "bit" complex). It is not worth to spend time on such for MP1 as the MPII has already much more flexible skinning engine thanm XBMC.