Perhaps the function should be called `-reinstall', or `-reactivate',
but I am uncertain about all these names too.

> Ignoring the refresh woes, I suggest the following design changes:
>
>   - allow strings in `-selected-packages' if possible

Can be done.

>   - make `-ensure-packages' interactive for `M-x'

Can be done.

>   - rename `-ensure-' to `-install-selected-' for consistency

Can be done.

>   - auto-load `-install-selected-packages' for common use

Not a fan of that, but I guess it can be done.

>   - rename `-refresh' to `-update' for consistency

That would be wrong, because `package-vc-refresh' doesn't update the
package.  There is `package-vc-update' and `package-update' (that do the
same thing for source packages).  Maybe `package-vc-update' can be made
interactive too and made to only prompt for source packages.

>   - add `-update-all' for consistency

That already exists, in `package-update-all'.  It will also update
source packages.  What you have in mind would be a
`package-vc-update-all' that would only update all the source packages.

>   - fix the nonexistent function reference in the documentation

Right, we are on that already.

> Then, the existing users of `package.el' will know how to use a large
> part of `package-vc.el' without needing to learn that "ensure" means
> "install-selected", "refresh" means "update", and so on.

I agree on these points.

> Rudy