The genius of this sonnet is fairly remarkable. I had a few morbid thoughts in relation to it, which I'm going to commit to this humble blog entry.
In the first three lines, Shakespeare compares love to a disease, but the most amazing thing about it is that he feeds the illness willingly, which represents the masochistic aspect of it. The fourth line admits that body has unhealthy appetites. The twist I propose is to imagine disease and decay of the body as the literal objects of love. The disease provides altered conditions of the body and mind, which often were deemed as sacred and holy. For instance, in On the Sacred Disease, one of the works of Hippocratic Corpus, written in 400 BCE, author opposes the sacredness of what is thought to be a first description of epilepsy. Hippocrates disagrees with the common opinion of the time, which calls epilepsy sacred. I don't want to call disease sacred in a superstitious sense or pertaining to Christian God. I want to view the disease as a god on and of itself. Deterioration, decay and disease for some reason entail such greatness that they must be sanctified. Your body slowly deteriorates like a flower that is prepared for the herbarium; like human skin, a petal drys and slowly deteriorates becoming a messenger of sorrow and autumn. Instead of lively pink we have a more complex, beautiful and eternal texture of art and dark piety. In other words, I want to glorify the aesthetics of decay by sanctifying it and giving a divine status.
Sadly, there are few primary sources where disease is viewed as sacred or where the decay is sanctified. In Finnish mythology, for instance, there is a goddess Kalma, which represents death and decay. Little is known about this goddess, but the precedent plays important role. Kalma was believed to be in charge of disintegration of bodies. Once the process was finished, souls of the dead would leave their fragile vials and proceed to the Kingdom of Manala. The Kalevala mentions Kalma very few times. From that I could deduce that this goddess leaves in the underworld and is in possession of certain plain where castles and halls can be found (also belonging to Kalma). It is considered an honor for the body to decay or "laying on the lap of Kalma", which is stated in the dialog between the messenger and Kullerwoinen (son of evil):
"Lo! thy brother too has perished,
Dead he lies within the forest,
Manalainen's trumpet called him;
Home return and do him honor,
Lay him in the lap of Kalma."
Kullerwoinen thus replying:
"Has my hero-brother perished,
There is home a sable stallion
That will take him' to his slumber,
Lay him in the lap of Kalma."
In the same way perished Kullerwoinen's sister and mother. Full text can be found here: http://www.sacred-texts.com/neu/kveng/kvrune36.htm. Among other things, Kalma would guide spirits to the afterlife and lurk around cemeteries. The aspect of decay in itself, however, is not elaborated at all.
Less authoritative (or inspiring) source comes from the imagination of game creators, in particular Forgotten Realms universe and its goddess Talona, whose symbols are that of disease and poison. There is book called Lady of Poison by Bruce Cordell, which is so badly written that I wasn't even able to finish it. It doesn't detail the priesthood of this interesting goddess (dedicating only about 20 pages to it) , but it at least sets a modern precedent of human thought that arrived in its development to sanctification of death and disease. It is very possible that the creators of said imaginary world have drawn their ideas from Finnish mythology, because there is a goddess Loviatar that bears the same name both in the game and its primary source.
Sonnet 147 may serve as a guide for the imaginary followers of Kalma or Talona. The elegance of Shakespeare sounds like a piece of divine text or verse. There are some interesting and twisted passages in existing sacred texts, such as Bible, where Paul the Apostle, in his Second Epistle to the Corinthians 12:7–9 (my favorite quote from the Bible) says: "Thorn in thy flesh was given to me, a messenger of Satan to torment me, so that I would not become conceited." (This is not any particular translation; I compiled it from different once, because Satan sometimes is called angel of death or adversary, while instead of the word 'torment' some versions use different words, which don't sound as exhilarating). Someone might argue that masochism was embedded in Christianity by the very deed of Jesus Christ. Paul's message is directly related to the idea of sacredness of the disease or "thorn", which serves as a tool sent by Satan, but obviously ordained by God to inflict potentially painful and damaging wounds. These wounds, however evil, are still directed towards the good end. Again, another favorite theme of mine, i.e. evil does good or is directed towards the good end. There's a whole book dedicated to the idea of the disease and this biblical passage by by Andrew Crislip called Thorns in the Flesh: Illness and Sanctity in Late Ancient Christianity, which I'm yet to read.
Photo of thorns is by me; the whole series can be found here: https://www.behance.net/gallery/12439707/Thorns