Congratulations to Autumn, Peter and Savannah!
Isla Elizabeth is a very beautiful name.
Artemisia, that's an interesting list of reigning Queens' names.
I don't think there would be any need to duplicate them, however.
If Beatrice, for example, were to become Queen her name would be legally acceptable - wouldn't it? I think that 'Savannah' might even be legally allowed should, God forbid, some terrible misfortune overcome the rest of the Royal family. Does anyone know whether only certain restricted names are accepted for a regent?
Thank you.
As far as legal part of this comes, there is no restriction to the Monarch's name. Queen Victoria's name was quite regal and although there had never been a previous Monarch with the name, it was accepted quite easily (even though initially it was thought she would reign under her first given name - Alexandrina). Beatrice is certainly royal enough to similarly encounter no difficulties.
There could even be King Pilot Inspektor or Queen Princess Tiaamii for all it matters; however, in case of the more exotic names, it is likely a more regal-sounding name will be chosen as the regnal one. For example, if Isla Elizabeth were to become Queen, she would probably choose Elizabeth as her regnal name; that wouldn't be unusual since most Monarchs starting from Queen Victoria actually reigned not under their first, but one of the middle names. A Monarch is free to choose one of his/her middle names as the one he/she would reign under, or a completely random name altogether.
Prince Charles, for example, could reign under any of his given names - as Charles III, Philip I (or Philip II, depending on whether Philip of Spain - Mary I's husband - is accepted as King Regnant of England, which he was for the duration of their marriage), Arthur I, or George VII. Alternatively, he could become Edward IX, Henry IX, Robert IV, or Francis I - any regnal name he'd choose.
The royal families are all about continuity; choosing a first name for the Heir with strong royal connections, probably one that had belonged to previous Queens Regnant, would be the logical (but not obligatory) thing to do.