Of all the oil leagues, the Saudi league is now on a much higher level than Qatar/UAE/Kuwait etc.
Based on their ACL performances you’d put the quality of the Saudi league probably on par with the K-League i.e. a higher level than the A-Legue, but obviously not J.League level.
He can definitely aim higher, however it wouldn’t be the worst move in the world tbh, and being located in Asia would be beneficial too for Socceroos travel.
As mentioned, as a GK he’d be facing world-class strikers almost every week, as most of the marquees in Saudi are attacking players.