yes. I.e., mimic `np.array`
```
copy : bool, optional
    If true (default), then the object is copied.  Otherwise, a copy
    will only be made if __array__ returns a copy, if obj is a
    nested sequence, or if a copy is needed to satisfy any of the other
    requirements (`dtype`, `order`, etc.).
```
A use case would be for the `.to` constructor (and `.si`, `.cgs`, perhaps `.decompose`), where one could also add `copy` (or @wkerzendorf's `inplace`). It would also allow one to remove some of the assignments to `_unit` (e.g., in `__imul__`)