It’s interesting isn’t it because while the likes of Harry and Andrew can have their titles changed, patronages removed, honorary commissions resigned etc. and not be ‘working royals’, you cannot remove who they were at birth and so there are going to be a few things, like this, where it still has to be them
Harry could be suspended from the role under existing arrangements, for as long as he is domiciled overseas.
I cant see any reason why Andrew could not relinquish the role himself, but he can't be sacked from it. It's controlled by law and would need Parliamentary agreement of some sort. The next two adults (over 21) are Beatrice and Eugenie.
It would require a change in the law to alter that. Then Edward, then Anne. (Then Peter, then Zara)
So much as we might have the 'magnificent seven' doing the duties, they can't be the counsellors of state
One possible variation would be to seek parliamentary approval for Camilla to become one even before Charles accedes. As she is likely to become one early in his reign, then it's only a minor variation on timing. I'm not sure if there is any provision for spouse of a regent (because those circumstances aren't covered), but it would make sense for them to be treated as consort