Change caption label delimiter with babel french in memoir but without caption package?

The following memoir document includes the french option to babel.

Is it possible — without using the caption package — to force use of the caption label delimiter that I specify with captiondelim?

documentclass{memoir}

usepackage[french,main=english]{babel}

captionstyle[centering]{}
captionnamefont{sffamily}
captiondelim{textsf{.,}} % note delimiter!
indentcaption{0pt}

begin{document}
mainmatter
noindenthrulefill

{changecaptionwidthcaptionwidth{3in}%
begin{figure}[htb]
centering
framebox[8.25cm][c]{rule{0pt}{2cm}}
caption{A very long caption. Blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah}    
end{figure}
}
normalcaptionwidth

begin{figure}[htb]
centering
framebox[10cm][c]{rule{0pt}{2cm}}
caption{A very short caption.}
end{figure}

end{document}

As the output shows, the caption delimiter has been changed from my specified period to a colon, and I know this is because babel has the french option.

I am aware of the caption package, which could be used to correct that. However, I do not know whether, or how, caption would allow on-the-fly change of the caption width as is possible with memoir‘s built-in commands changecaptionwidth and normalcaptionwidth.