I like it. It's a little stodgy, but charmingly so. I just love its eighteenth century flavor. And no, I don't think
Marty is at all inevitable. In fact, it's never even occurred to me as a nickname for
Martha.
Martha has had some nicknames --
Mattie,
Patty, and
Patsy -- but these date from the eighteenth century, when
Martha was so common that nicknames had to be found to differentiate between the girls and women named
Martha. I don't think any nickname is even likely these days.