Currently mpich2 includes alternatives support. It MUST either be removed, or moved to a subpackage.

If you decide to go with the alternatives support subpackage, then you also need to figure out how to add the MPICH2 directories to the path. When doing that, you need to remember that the libraries have to be useable, too.

I personally would suggest dropping alternatives support altogether, and replacing it with a subpackage that makes the mpich2 module be loaded automatically by placing a few files in /etc/profile.d.