I don't think you can get the virtual methods from both interfaces with this module.
As far as I understand, Class::Virtual relies on accessor methods to implement static data members and does not try to 'merge' multiple parent class data. Which means, in case of multiple definition of the same data member you get whatever comes first in your class isa call path.

What's your rationale for wanting a template constructor? This looks interesting to me, since in Perl you don't usually ask for an explicit genericity mechanism.