A new street and snow or dirt circuit and I'm okay here.
Thought I can be a little specific with that:
Some Southeast Asian circuits, Sepang is one I really like to race in, maybe add a street circuit in a city (Singapore GP can fill that if no other city can fill it), although to keep the series away from too many F1 related circuits, perhaps a new Singapore configuration utilizing Orchard Rd for one section. Then there's my selfish request of my hometown city of Jakarta as a street circuit, especially for the fact that maybe 85% of the GT6 car list don't exist in the country alone in real life, so the course can answer a "what if" question where all the rarest and latest cars in the world drive in a city where 85% of the car list never even exist there.
Don't know about Sentul as it is a FIA Grade 2 circuit so nothing special exists there. Then there is more need of Northern European, African, and Middle Eastern tracks, any type would do.
I would be grateful if more Course Maker themes are supported throughout time in DLC, seeing a newly revised Course Maker will open more opportunities for more backdrop settings and road textures, to match the mood of the course where people use the GPS feature to create a circuit as it was intended.