Sorry for the late reply, but I don't think Class::MethodMaker will do this for you.
in reply to work around for static vars and singleton constructors not inheriting properly?
My Class::MakeMethods module does have something close to what you want:
'instance' => 'my_singleton',
'scalar' => 'my_static';
Those methods store a value in a per-class package variable, so each subclass and its instances share a common value without influencing the superclass and other subclasses.
For the static method, if you'd like the subclasses to default to sharing the superclass value and only override it in a few specific subclasses, use Template::Inheritable instead of Template::ClassVar.
I haven't tested the combination of Template::ClassVar and instance; please let me know if it doesn't work as expected...