Well, there's already one Frenchy in the family: H.R.H. Henry William Frederick Albert. (Everyone seems to've forgotten that his real name actually is NOT "Harry".) But Louis, please, no. I realise it would be an homage to William's granduncle, Louis, Earl Mountbatten, but William's father already did that with him: H.R.H. William Arthur Philip Louis. No need to continue that into another generation.