Exorcism is on the rise, according to this Guardian piece. The Vatican set up a new training scheme for would-be Von Sydows, claiming that reported instances of possession have grown exponentially in recent years. Evangelical churches have always been fond of exorcism, and there are independent exorcists that will bell, book & candle you for less than the price of a second-hand car. Or so the Economist claims.
Of course, there are no reliable statistics for any of this. The people reporting a rise in demand for exorcism are the same people who want to hold more exorcisms. The evidence is anecdotal, but that's never stopped anyone from jumping to a conclusion before.
Christianity has traditionally had a very uneasy relationship with the Devil, but not for the reason you might think. It's a power problem. If the Devil is capable of performing miracles, then what price God? In order to keep God at the top of the hierarchy, the Devil cannot perform miracles. His imps and minions can only perform natural acts, because if they could actually pull off supernatural stunts then the fine line between God and his opposite number gets blurrier than philosophers like. Instead they manipulate Man to achieve what seems to be miracles, but are not.
For the Dog of Hell is bound, writes one philosopher, neither can he operate on Forms, the Bodies of these, or their properties, unless he take to him the mind of Man as a co-operatives with him, under whose convents he bond-slaves by deceit, and binds them in a Covenant ... For he persuades those who have renounced Divine Grace, of whatsoever he will. and promiseth that he will perform Mischievous or wicked Acts, by strength or faculties which he feigneth to be natural or proper unto himself. For he snatcheth his Imps into the detestable adoration of a He-Goat, as if the government of all things stood in His power, and that he alone could confer the gift of the working of miracles.
The larger problem - and again, this was true in the medieval period as now - is that once you let the Devil in the door, there's no keeping him out. He's the original Special Pleading. There's no justifying him, but once you admit that he could be lurking in the shadows causing mayhem then there's no way to tell the difference between reality and the Devil's fantasy.
Moreover an exorcist, particularly an amateur, is likely to look at almost any problem as a spiritual one requiring immediate spiritual intervention. Not, say, a problem of human fallibility, or a medical problem requiring medical assistance. The same is true of their petitioners. Very few people understand what exorcism is, but if it doesn't look like Netflix crossed with Hammer Horror and offer a convenient one-stop cure for their problem, they don't believe it.
Phil Rickman's Merrily Watkins series about a female Deliverance cleric operating in Hertfordshire makes this point again and again: it is all too easy to become addicted to exorcism, to see it as a solution to problems it was never meant to handle. Merrily often has to discourage people from thinking of her job as an immediate cure, like calling out the plumber to deal with a leaky faucet.
However from a role-playing POV, and with one eye on Pelgrane's Night's Black Agents, an exorcist player character has appeal. Moreover Merrily Watkins has a hint as to which way it should go, as the series is set near Hereford, the home of the SAS. Often a character in one of her mysteries turns out to be a former SAS now retired, or turned priest. You can see the appeal for a serving soldier; first-hand combat experience often either turns a person atheist, or devout. Muscular Christianity offers the willing a chance to fight spiritual problems with physical action. What more could a former special operations vet wish for?
That said, designing a character template for this ought to take the civilian version into consideration, the occultist with a yen for theatrics and a PayPal account for donations. With that in mind, here's two options for an exorcist player character.
Exorcist (Former Soldier)
Investigative: Intimidation 2, Military Science 1, Occult Studies 2, Outdoor Survival 1. Possible alternates: Urban Survival, Vampirology.
General: Athletics or Shooting 10, Hand-to-Hand 4, Preparedness 4. Possible alternates: Sense Trouble, Weapons.
Exorcist (Enthusiastic Amateur)
Investigative: Bullshit Detector 1, History 2, Occult Studies 2, Research 1. Possible alternates: Vampirology, Diagnosis, Reassurance
General: Conceal 6, Shrink 6, Preparedness 6. Possible alternates: Filch (for those who like to take their theatrics one step too far).