Good point about
Mary Rosamund and the 'r' sound. I hadn't thought of that, and now that you mention it it's bothering me!
My favorites from your list are:
Mary Violet - so, so, so good.
Mary Diana - beautiful.
Mary Colette - I wouldn't have thought of
Colette, but I really like this!
Mary Genevieve - lovely!
Mary Delphine - beautiful!
Your list also gave me the idea for
Mary Gwendolyn, with which I am now in love.
Thanks very much for your ideas!