here we go
https://gbatemp.net/threads/pok%C3%A9mon-nova-sun-umbra-moon-fully-featured-challenging-sun-moon-romhacks.462295/Same author as Rutile Ruby/Star Sapphire if you've played those, easily my favorite romhack I've played
Level curve balanced for exp share
Actual challenge (trainers have well built teams with real sets), requires strategy and proper team building to get through rather than just grinding