[name_f]Yseult[/name_f] is lovely - frosty and magical.
The authentic [name_m]French[/name_m] pronunciation is “ee-zeuh” (you can listen to it on Forvo), which takes away the “insult” and “assault” problem, and in my opinion sounds even more sparkly and alluring than the anglicised pronunciation.
I really like [name_f]Yseult[/name_f] [name_f]Morgana[/name_f] [name_f]Constance[/name_f], but [name_f]Yseult[/name_f] [name_f]Morgana[/name_f] is doubly Arthurian, so I would go with [name_f]Yseult[/name_f] [name_f]Ophelia[/name_f] [name_f]Snow[/name_f] instead.
[name_f]Tabitha[/name_f] is also beautiful, and I’m very happy to see that you actually considered [name_f]Hephzibah[/name_f], even though you aren’t going ahead with her.