No to a republic and no to Prince Charles (or King George as he will be) airing his opinions...unless they are very anodyne opinions about, say, the weather.
He absolutely cannot air political opinions. The role of constitutional monarch forbids it.
Once he aligns himself with a particular party, or political viewpoint, the monarchy will be sunk.
Sure he can have opinions, but he can't publicise them.
He's also not allowed to vote.
I assume the palaces, jewels and weekly roast swan make up for that.