putting '/' at the end works by just removing the ../ or / prefixes from the link text. so [[../../a/b/]] becomes a/b. isn't it more logical for it to become 'b'? the meaning of '/' at the end then behaves like 'basename' shell command.
to achieve this, in Parser::maybeDoSubpageLink, i changed the lines '$text=...' to '$text = array_pop(explode('/', ...))'.