The breakup of his marriage and the circumstances and parties involved continue to be relevant no matter who's living or dead.
Would you like to back that up with a statement from the Church about it? Because the CofE site says:
1.8 Entitlement to marry. Any person of British Nationality who normally resides in England is entitled to marry in his or her Church of England parish church, provided that (1) the other partner is also of British Nationality and also normally resides in England, (2) that there are no legal impediments of the kind described below [Section 6], and (3) that neither of the couple is a divorcee
whose previous partner is still living (the Church of England's regulation on this matter is recognised in law [Matrimonial Causes Act 1965, s.8] - see below, section 10.1). This entitlement applies irrespective of whether either of the couple normally attends church and irrespective of whether either of them has been baptised. It also applies irrespective of whether either partner is a member of the Church of England, or of another denomination (or of none) [but see paragraph 10.4 regarding the marriage in church of persons of non-Christian Faiths]. However, the entitlement only applies to the parish church of the person concerned, and does not extend to any other Church of England churches (for which additional requirements must be fulfilled - see Sections 3 & 4). [emphasis added]
http://www.cofe.anglican.org/lifechanges/index.html
http://www.cofe.anglican.org/papers/mcad.htm
As I said in a previous post, I think that Charles ought to be held to a higher standard by the church because of his position as head of the church when he becomes king. I think the Archbishop would have every right to refuse to crown him if he continues in his present situation, although the present Archbishop probably wouldn't force the issue.
I do think it's interesting however that you inadvertently admit that Prince Charles has never had an honest discussion with his grown sons to this day about the facts of his marriage. That says a lot not only about him but about the true state of his relationship with them.
I'm not just saying that. I'm saying that neither son was around before the marriage and during the honeymoon, neither son was capable of understanding what was going on for several years after their birth, and neither son was an eyewitness of every single thing that happened even when they were old enough to understand. Therefore, most of what they know was told to them by their parents or other partisans on both sides. There's no way for us to know if Charles, Diana, or both had discussed things with their sons honestly or just tried to present their own sides of the problem in order to get the children to side with them against the other parent.
Prince William is going to become the British head of state. He's being trained for it by the Queen, and he's going to have to pay attention to the senior members of the royal household and the government; he isn't going to be able to do anything he wants. The fact that his parents were two very different people is irrelevant. He isn't going to be able to indulge his own feelings - even assuming he has them, which he very well may not - and turn the monarchy into some sort of tribute to Diana.