It's one thing for a club to have prolific attacking players but a different thing to have a strong defense line. Al Nassr have the former but doesn't have the latter and that's why they failed to win any major trophy this season despite having striker like Cristiano Ronaldo who was easily the highest scoring striker in the league and in the whole of Asia in the just concluded league. Al Nassr like you rightly said have the financial strength to sign the best players in the Saudi Pro League so I think they'll definitely strengthen the club's defense line ahead of next season. If they can have a good defense line that rarely concede goals while having an attacking line that's scoring goals for fun, Al Nassr will definitely be a club to beat come next season. Cristiano Ronaldo isn't happy that he couldn't win a major trophy with the club in the just concluded season and if the club doesn't make major signings that'll help improve the team, the Portuguese superstar might just leave the club any time soon because he loves winning trophies and that I don't think the club management will ever want to happen.
Of course Al-Nassr have everything it takes to be able to purchase some great players and build a very reliant squad especially building up their defense line and also midfield strength. They have a fierce attack especially with Ronaldo and Mane upfront you can get confidence of their attack but the issue now still remains the leaking defense.
One of the greatest character of a winning team is having a well secured and protected defense line because it helps you stay safe without conceding goals. With an attcker that scores goal like Ronaldo, a great one thing to do will be to build and invest solidly in the defense of the team as that would help the team build up on the goals scored rather than goals conceded.This in mind, I think the club can focus more on trying to sign up quality defenders and yes they have the necessary funds to necessitate on that.
They will also be needing a very strong midfield player or players so as to help the defense line and also feed the attack line of the team. The club will be acting very fast because they know Ronaldo might be running out of time as he loves winning trophy and going another season without a trophy might mean him getting out of the club to where he can win trophies. The club needs to do something fast about their situation to still be able to keep Ronaldo in the club.