I won't take this too seriously because Ruud van Nistelrooy is not someone who has experience in the coaching field so I don't think the impact will be too big if Manchester United management appoints Ruud van Nistelrooy as Ten Hag's assistant.
Manchester United's management built this team as if they didn't have a clear plan, now they trust Ten Hag too much and always fulfill Ten Hag's wishes in recruiting players, but Ten Hag has not succeeded in improving Manchester United's performance.
But now we see that they are going through a process and we have to respect and also wait for the results of this process.
Few things are never been look good or as we want, but these are having big impact on few players and teams for improving their performance same happening in this case right now we all know Manchester United is having few top players which can do much better than expectations, and they are not able to do on this way so having legendary player like Ruud Van Nistelrooy is surely going to have good impact on their performance, and we can expect better results from their strikers which are best.
Here I am agreed as they are building their team without any plan, but you can't expect anything good with long term strategy from the business mind peoples like Glazers which are running this club for years but fail to bring good results which is surely their failure.