There are plenty of Shakespearean names that are poetic and beautiful but not seen as massively 'out there'. Thisbe is definitely not one I'd go for. It sounds ugly to me. And yes, lots of children (and some adults!) can't say th so it would become Fizzbee ... which suddenly sounds quite sweet to my ear now I've written it down but still isn't what you want for a name!
I love Xanthe. Romy is lovely too.
Otherwise, as a random collection of Shakespearean/Greek/Celtic/writing-linked/European sounding names, how about:
Ariadne, Aurelia, Amaya, Ariel, Athena, Aurora, Amity, Aphra, Alyona
Bronte, Bronwen, Beatrice
Calliope, Cassandra, Clarissa, Cordelia, Calista, Celyn, Carlotta, Cadence
Delphi, Daphne, Demelza, Drucilla
Evadne, Elowen, Eden, Elisaveta, Electra, Ebony, Evangeline
Fenella, Fabia, Francesca, Fleur
Giselle, Genevieve, Guinevere
Hermione, Helena, Honor, Harmony
Isabella, Imelda, Isadora, Inez, Iona
Jacinta, Jessamy, Juliet
Karensa, Keziah
Lorelai, Luana, Liara, Livia, Leonie, Luna, Lyric
Miranda, Morwenna, Maeve, Marissa, Melinda, Melody, Minerva
Neriah, Nyah, Nova
Octavia, Ophelia, Odette, Ottilie, Ondine
Persephone, Phoebe, Phyllida, Pandora, Paloma
Rosanna, Reagan, Ramona, Rhiannon, Rosina, Rowena, Raven, Rose, Raine
Sylvia, Serena, Seren, Saskia, Seraphina, Susanna, Summer, Sephora, Story
Thalia, Tamara, Thea, Tansy, Taryn, Talitha, Tabitha, Tallulah
Viola, Vivienne, Vanessa, Verity
Xanthippe, Xenia
Yolanda, Ysanne
Zeryn, Zillah, Zola, Zelda, Zipporah