Will it be possible to specialize `std::optional` for user-defined types? If not, is it too late to propose this to the standard?

My use case for this is an integer-like class that represents a value within a range. For instance, you could have an integer that lies somewhere in the range [0, 10]. Many of my applications are sensitive to even a single byte of overhead, so I would be unable to use a non-specialized `std::optional` due to the extra `bool`. However, a specialization for `std::optional` would be trivial for an integer that has a range smaller than its underlying type. We could simply store the value `11` in my example. This should provide no space or time overhead over a non-optional value.

Am I allowed to create this specialization in `namespace std`?