I much prefer the spelling Joni. Well recognised due to Joni Mitchell and looks like a name in it's own right whereas Joanie looks like a cutesy nickname for Joan which I think is old lady rather than old lady chic tbh.
Not keen on June. Love Juliet
I don't know whether your style is old fashioned/retro or cool/quirky. Joni and June kind of sit in the middle. Ummm, how about:
Avis, April, Aphra, Astrid, Bronte, Bonnie, Bess, Betsy, Cora, Coco, Daphne, Diana, Esme, Edith, Flora, Gloria, Hazel, Hetty, Ida, Inez, Judy, Jocelyn, Joyce, Jonna, Jamie, Jessa, Kezzie, Kelly, Lorna, Laurel, Lena, Lennie, Lois, Maeve, Mabel, Maude, Mavis, Mimi, Nina, Nora, Nell, Nancy, Opal, Pearl, Polly, Penny, Ruby, Rita, Rosa, Rhona, Ramona, Sylvie, Susie, Sadie, Tessa, Tara, Thalia, Una, Vera, Veda, Verity, Viola, Willa, Winnie, Yvette, Zelda