I agree with you about the "technical" part. However, given all the talk from Charles about wanting to cull down the HRH part …. just wondering if it's only lip service. After all, the Cambridge's have 3 kids … Harry is no longer a seat warmer and his children even less so. JHMO.
I believe that after HM's death Charles will need William's support in more official things in the UK while he will use Harry's help for tending to the Commonwealth. Maybe, if Britain takes a bit of a fall following Brexit, they might even send the Sussexes to Australia, to represent the king there as governor general, to keep Australia closer to Britain. So I believe Harry will be important and his children, too. Probably even James Severn, who, when (as it is planned) his father becomes Duke of Edinburgh after Philip dies and Charles ascends the throne and creates the title anew for his brother, and James will become Earl of Wessex, he will be probably helping his father with Philip's charities and award scheme, just like Edward took over when Philip retired.
Surely Louise, Charlotte and Louis will have a chance to not become working Royals, but I think if they want to be, they could.
The problem for the York-girls IMHO has always been the combination of Andrew & Sarah behind them. I am sure Charles knows exactly what kind of business deals Andrew has organized on playing golf worldwide and or when he was a trade representative. (Sarah was so sure when she was caught by the fake sheikh that she could introduce him to Andrew and that Andrew would do "something" for him - this was IMHO not the first time the Yorks played that game without the palace being aware of what was going on. So I think Charles just shuddered at the idea that Beatrice and Eugenie would follow their parents, especially when Andrew took Beatrice with him to the Arab countries to "introduce" her.
But Edward needs someone to follow him and there is enough work even for both of his kids and the Commonwealth could be a chance for the Sussexes' kids.
IMHO, of course.