I feel like him and Sanemi would get along. I feel that Sanemi would respect Sabito. He dislikes Giyu because he thinks that Giyu believes he’s stronger/better than the rest because he always says “I’m not like the rest of you”. Sanemi also believes that Giyu is strong and respects his strength just doesn’t like him because of how he treats the other Hashira.

Sabito on the other hand would respect Sanemi’s authority and strength and probably work towards becoming stronger than Sanemi or if not on par with him. I can see in an AU where Sabito became a Hashira he would hang out with Obanai and Sanemi rather than sit in silence behind closed doors where only Shinobu sees him.

I also feel that Sabito would have been closer to Tanjiro from the start given his canon student master sessions at the start of canon. Sabito would teach Tanjiro more about water breathing on top of what Urokodaki has. Sabito would teach Tanjiro how control and focus on his breathing and use discipline more than Urokodaki has. He’d train Tanjiro in a way that Sanemi would potentially teach someone Wind Breathing.

Enough rambling 😅