I love
Laetitia.
Letitia is the more common spelling here in the U.S. But the "ae" version is definitely more interesting / intriguing.
Your pronunciation is also my preferred one. But I haven't a hope of getting away from the "tish" pronunciation here, not that I mind it that much. Your pronunciation would probably work in a Latino community here, but not elsewhere. If it really bothers you that much, then I would keep it in the mn position.
I believe the
Leticia spelling is Spanish, but I could be wrong.