We will get back to solve this problem once Moodle 2.6 version is OK which should be this weekend.
We need to agree that the main use of the actual numerical questiontype is to grade the number value within a +- range and not the way the numerical value is written. This should be the more flexible as it could be without breaking the millions of already existing questions.
New question types have been developped at Open University (OU) that complement the "historical" numeric and calculated question types by adding new features like grading the number format. They can be added to your local moodle installation.
Pierre