I'm actually a fan of the Ghost/Dark type here. Beyond it being the spookiest type, it is often overlooked since it is a largely neutral typing with just about as many downsides as it has up, but I think it's worth taking a look at what it provides.
Obviously with Shadow Force being the typing of choice, we want a ghost typing to provide STAB, since ghost is not a particularly good coverage typing. Making SF be a move that the opponent fears to switch into is what it should strive for I feel. The dark type part of the typing neutralizes ghost's weaknesses, provides a psychic immunity for pesky stored power shenanigans, and the ghost part of the equation nullifies one of dark's biggest weaknesses. The Dark typing does however give it a neutrality to bug, and adds a weakness to fairy. The important mark is the neutrality to dark, since that typing would be the most willing to switch in, what with the lack of normal types to do the job. Dark neutrality means that we aren't immediately forced out when a dark type comes in to tank a SF, which means the pummeling can continue if we have coverage to handle it, or if our SF is particularly powerful. Offensively, the dark type gives us stab on very strong options in sucker punch and knock off primarily. Sucker punch being a strong priority to combo well as a 1-2 punch with a shadow force that goes last, and Knock Off being one of the best and most spammable moves in the game, providing item removal to make SF sting more. Dark moves here would be arguably pretty safe to use since the worrisome move coming off of the mon should be Shadow Force first and foremost, and the mons that resist dark moves (aside from other dark types) such as Arghonaut, Cresceidon, and Great Tusk probably would not appreciate taking the hit.
The downsides of the typing offensively is that dark rubs up against a lot of shadow force's strengths and weaknesses offensively, ghost already hits plenty for neutral damage, and dark hits the same typings super effectively, while also being resisted by more. And Dark doesn't help at all offensively with ghost's dark resist. Kingambit, Ting-Lu, and Hamurott switch in very relatively easily and devour the typing if we don't have any further coverage. Additionally, with Shadow Force being the move of choice to build around, the dark moves we would have to choose from would be overshadowed in pure power, and don't provide a coverage boost to be used alongside items like choice band, limiting our item selection a bit. Defensively, the typing is famously a largely neutral typing across the board, which makes it a pretty good type for a stat stick if we choose to do so. It is however very weak to fairy revenge killers, Hemo and Iron Valiant check the typing extremely well.
Obviously with Shadow Force being the typing of choice, we want a ghost typing to provide STAB, since ghost is not a particularly good coverage typing. Making SF be a move that the opponent fears to switch into is what it should strive for I feel. The dark type part of the typing neutralizes ghost's weaknesses, provides a psychic immunity for pesky stored power shenanigans, and the ghost part of the equation nullifies one of dark's biggest weaknesses. The Dark typing does however give it a neutrality to bug, and adds a weakness to fairy. The important mark is the neutrality to dark, since that typing would be the most willing to switch in, what with the lack of normal types to do the job. Dark neutrality means that we aren't immediately forced out when a dark type comes in to tank a SF, which means the pummeling can continue if we have coverage to handle it, or if our SF is particularly powerful. Offensively, the dark type gives us stab on very strong options in sucker punch and knock off primarily. Sucker punch being a strong priority to combo well as a 1-2 punch with a shadow force that goes last, and Knock Off being one of the best and most spammable moves in the game, providing item removal to make SF sting more. Dark moves here would be arguably pretty safe to use since the worrisome move coming off of the mon should be Shadow Force first and foremost, and the mons that resist dark moves (aside from other dark types) such as Arghonaut, Cresceidon, and Great Tusk probably would not appreciate taking the hit.
The downsides of the typing offensively is that dark rubs up against a lot of shadow force's strengths and weaknesses offensively, ghost already hits plenty for neutral damage, and dark hits the same typings super effectively, while also being resisted by more. And Dark doesn't help at all offensively with ghost's dark resist. Kingambit, Ting-Lu, and Hamurott switch in very relatively easily and devour the typing if we don't have any further coverage. Additionally, with Shadow Force being the move of choice to build around, the dark moves we would have to choose from would be overshadowed in pure power, and don't provide a coverage boost to be used alongside items like choice band, limiting our item selection a bit. Defensively, the typing is famously a largely neutral typing across the board, which makes it a pretty good type for a stat stick if we choose to do so. It is however very weak to fairy revenge killers, Hemo and Iron Valiant check the typing extremely well.
