Dialects are of limited uses, because they are dialects... New dialects are arguably of even more limited uses, because better languages now exist where the desirable characteristics are enforced not by using a dialect, but by the core languages, and safety checking is not optional. (Also, I'm somewhat curious about why the proposed dialect tells about think "similar to unique_ptr, and so over: just use the real think -- at least it would be less a dialect and more of modern standard C++). Dialects enforced by wishful thinking or at beast ad-hoc tools maintained by a too small community will perish in front of well architectured languages maintained by a real community.
They have even been used to ship some important code in big project made of tons of legacy code -- so I'm not even sure an interop argument could be made.
One point of a dialect (aka “coding standards”) is that you can evolve legacy code bases toward them with a series of simple refactorings instead of by rewriting from scratch.
For me this is the big advantage of C++: it is possible to backport virtually any language feature you want to it, thanks to the combination of modern template programming and low-level C-style bit twiddling.
They have even been used to ship some important code in big project made of tons of legacy code -- so I'm not even sure an interop argument could be made.