Your post just made me decide to like it.
I've only personally known one
Mary who was my own age, so I haven't had the experience that it's common, only the impression from having heard of so many Marys. And I like M-r names, and -ry ... so, why not?
I like
Marion a little more than I like
Mary.
I don't care for
Molly or
Polly.
I think it's okay spelled
Mari.
I also like
Marie and
Maria and
Mariah, but not
Miriam /
Mariam.
I would not use a double or hyphenated name, it's nms. I think
Mary combines well with other short common names -
Mary Anne,
Mary Beth,
Mary Ellen, and
Mary Jane are nice, and familiar enough to not sound stilted. I kinda like the combo
Mary Linda.