Very good deals with premium credit cards, friendly staff and the experience was ok.
Our plane (last of the day) arrived more than 1h late! Since we already agreed by email before, staff waited for us after opening hours which is a major +++. By experience, not everybody would have..
Security process can still be improved (25 usd of bank fees from debiting/crediting the deposit on my international card, all on the same day) but no problem in itself. Surely will be solved at some points.
No need for international driving licence for short stay in Jamaica.
Thanks again Sixt team for everything.