Funny when you say "And that's excluding the little but strong leagues like in Portugal & Belgium" because Matic was the BEST player in the portuguese league when he played there, not CM, best player of any position.
About the others, playing at Napoli/Lyon is different than playing for a top club, i don't watch a lot of Napoli/Lyon but it's a entirely different level being a starter for Chelsea, Nainggolan is probably a bit better but too expensive for his age. Fabinho is a good option but i like Saul the most of your list.
We need another option anyway for depth but Matic job's is not an easy task, so picking a player performing well from some mid tier club is not guaranteed sucess, Matic was a monster for Benfica, the standards here are totally different.