It hasnt been quite the quantum leap you describe. There were and remain many people who view Camilla the exact way that you describe Wallis and for exactly the same reasons, with the exception of it being one husband instead of two. On the other hand, Wallis was not famous for saying 'Your Great Grandfather', etc. Nor did Wallis come between Edward VIII and his Queen, only of course because he didnt have one... I am not selectively resurrecting anything. I am pointing out that in the exact same situation, in Charles' family in the last two generations,his Great Uncle, who was already King, was not permitted to marry 'the woman he loved' in the same situation. He was required to abdicate. His Aunt The Princess Margaret was also told she would have to give up her place in the succession and any income from the civil list, should she chose to marry her divorced lover . This is not something I am 'resurrecting'. It's called History and Precedent, something the BRF is loathe to disrupt. This is the same reason I find the 'They chose to have a civil marriage' argument unlikely.
I find this a bit off-topic, as we are discussing the fact IMHO fi the marriage of Charles and Camilla could be illegal because they did not marry in a church but a civil wedding. I understand it has been pointed out that in the Uk there are two possibilities of getting legally married: in a CoE/CoS wedding or in a civil wedding at the registry office. (It's different for example in Germany, only civil weddings are considered legally binding here).
Charles and Camilla chose the civil wedding because of reasons unknown to us. Speculation about their reasoning does not help to answer the question: is this way to get married legally binding? The problem that arises is that according to the wording of the Act which makes civil weddings legal this is not a possibility for members of the Royal family. But when it comes to laws, it is necessary to look into all their details to see if they are according to the main principles of law valid in a country. If not, these articles are not legally binding. As the exception of a group of people due to the circumstances of their birth from rights accorded to all others in the country is illegal under the main principle of "equality" in the EU-law about Human Rights which is valid in the Uk, the laws barring Charles from getting married in a civil wedding are void. Thus, Charles and Camilla are legally married.
The question if they could have married in church or not is absolutely of no juridical interest to Camilla's legal position as wife of The Prince of Wales.
As for the question about Charles' accession to the throne as a divorcee:
the law in the Uk has two requirements for a man or woman to become king or queen. He or she must be the heir of the souverain and be alive in the moment the predecessor dies. Charles is the heir of HM Queen Elizabeth the Second and we'll see if he survives his mother for more than a second. That sounds laughable but it's important in any case where an inheritance is involved. If two persons die for example in the same minute because of an accident but person One dies at 2:01:01 and person Two dies at 2:01:02 then person Two was for a second owner of person One's bequest if that is the line of succession.
In the law of the UK when it comes to the throne this is given by the fact that there is no interregnum. The moment the souverain dies, the heir becomes the next souverain. This may sound unimportant but it was discussed after queen Victoria's accession to the throne: what would have been if the widowed queen Adelaide had been pregnant at the time of her husband's death? As the law of the UK only accords rights to people born, the late king's unborn child would not have been his heir. As there is no interregnum the moment William IV. died, his heiress became queen. Okay, Queen Adelaide was not pregnant, so in the end this was a more or less theoretical discussion by the experts but it made the constitutional position on the acccession to the throne quite clear.
So: Charles and Camilla are legally married and Charles will be king if he is alive when his mother dies.