It is difficult to say - when a staff have been with a principle for long enough they accept how it works. There is a better drive towards that goal - as a team. Personally I think most of the problem with the Sussex is that they were working towards a different goal. Harry and Meghan were looking here and the team was looking there. No common viewpoint of what the office should have been working towards. And yes that type of alignment takes time - and is not helped by people leaving.
I was recently asked if the royal offices receive a mandate - if there is a single purpose coming from Charles office down. And yes there is. However the personal approach of the principal need to align to that mandate. Essential the office moves the royal according to the monarch's direction. Not the royal tells their office that this is how they are going to run things and then don't do any coordination with the other offices. I can understand why people think that the Sussex's were a loose cannon - running to crowd pleasing engagements and wanting to do politicized issues. It is just a complete lack of understanding.
I have a different take. In the case of Charles, I do not think that he has had enough time to set a mandate / single purpose. While there were duties, expectations and protocols, I don't think that there was a mandate / single purpose during QEII's reign beyond something broad like service.
I have been critical of the silos that were created during QEII's reign. Charles created his own office during his mother's reign, and IIRC it was motivated by him wanting to do things his way and not have to go through the BP bureaucracy, and because he had Duchy of Cornwall funding, he was able to do so. Years later, Charles set up a court for his sons when they were
teenagers, and IIRC, he was motivated by wanting to allow his sons to pursue their interests without being fettered by their father's staffers. Presumably this court was the forerunner of the KP organization.
The BRF have been criticized because for having the three silos and some years ago they merged their communications operations, but then split up again with Charles being the driving factor behind the re-split, IIRC. As previously stated, I have been critical of the silos, but I have to wonder that if things were more centralized, would initiatives like Heads Together, Invictus, Duchy Organics, The Earth Shot Prize, etc. have come together. I think The Prince's Trust was formed before Charles formed his own office, but would it have reached its current scale if Charles had not spun off.
I think that there are dysfunctional things about the way things were run but having adult grandchildren of the monarch will not be a common occurrence. I suspect that going forward that there will be a BP organization and, if there is an adult Duke/Duchess of Cornwall, that they will have their own organization, with presumably some kind of reporting relationship / coordination between the monarch and heir's organizations.
I just don't see Charles setting mandates for his reign and then expecting other royals and courtiers to adhere to that mandate. Yeah he may come up with some catchy mantra that pulls together and reflects values that the principals involved already possess, but I don't think that it is his nature to be too centralized. Plus I think that he is going to have his hands full transforming himself and his organization from the Prince of Wales paradigm into the monarch paradigm, because I do think that they are very different.
I think that unless Harry consigned himself to living a life of quiet desperation, he would have been a challenge to deal with had he remained a senior working royal. Harry left in a messy way and has continued to present challenges to the BRF from another hemisphere, but I don't think that he would have been easy to deal with had he stayed. I think it should also noted that things were in transition in the past few years, so even if you did not have the added complication of Harry getting married, there still would have been a rough road due to the distinction between him and William, which was already a sore spot, becoming more acute as time passed and not less.
To be sure, the Sussexes have shortcomings, but I think that there are lessons to be learned from this experience in handling spares. As much as people state that the monarch and heirs apparent should be paramount, the modern paradigm is just as much if not more royal family-centric as it is monarch - centric (IMO), and given that, should consideration be given to spares who have energy, ideas and popularity?