This doesn't address the final concern in the paper, removing the need to create two different names for the same thing.  ie In your example the two names `x` and `m_x` rather than just the one name `x`.

On Tue, Jan 14, 2020 at 3:15 AM Matthew Woehlke <mwoehlke.floss@gmail.com> wrote:
On 21/11/2019 05.33, Andrew Tomazos via Std-Proposals wrote:
> Please find attached a 2-page draft proposal entitled:
>
>      Proposal of constpub
>
> It seems a little thing but easy to implement and I think it may have broad
> appeal.
>
> Anyway, initial thoughts appreciated.
>     -Andrew.

I would rather see:

class foo
{
public:
  using x = std::as_const(m_x);
protected:
  int m_x;
}

No new keywords, leverages the idea of "universal aliases", has more
possible uses...

--
Matthew