It's harder to force switches offensively rather than defensively, since you're basically relying on your opponent to switch out for you to freely use Belly Drum. For instance, think of Lucario switching into Heatran. Will Heatran switch out in fear of Close Combat, or will Heatran stay in in fear of Swords Dance? This kind of mind-game is what I dislike about using offensive pressure to buy free setup turns. For this reason, I'm personally against any typing that produces said pressure because it's an unreliable tactic.
In order to guarantee setup whilst taking minimal damage in the process, you need high defensive pressure. This can be done fairly easily by having a typing that packs handy resistances and/or immunities and few weaknesses. Steel/Dragon isn't that great when you consider this because it's defensive presence is far inferior to its offensive presence. Sure it packs nifty resistances, but that's mostly due to the part Steel-type. Packing on a Dragon typing makes it take neutral damage from Fire, Ice, and most importantly, Dragon. This keeps it from being able to reliably set up against a potential Salamence locked into Outrage or a Choice Specs Latios's -2 Draco Meteor. You have to consider the most common attacking types out there. I mean, you're taking super effective damage from Fighting-type attacks now, making something like Scizor easily use Superpower rather than the expected Bullet Punch and Breloom or Conkeldurr to nuke you with priority Mach Punch. In fact, the majority of Steel/Dragon's resistances mean nothing when looking at popular Pokemon using said move. For example: it resists Gengar's Shadow Ball, but takes super effective damage from Focus Blast; it resists Terrakion's Stone Edge, but takes super effective damage from Close Combat; it resists Alakazam's Psychic, but takes super effective damage from Focus Blast; it resists Thundurus-T's Thunder and Hurricane, but takes super effective damage from Focus Blast; it resists Hydreigon's Dark Pulse, but will likely take upwards of 50% damage from Draco Meteor due to a neutral hit; it resists Keldeo's Surf, but takes super effective damage from Secret Sword. Also, the Water resistance can be nullified essentially under rain. I mean, you can probably do this with every other typing out there because these Pokemon are typically packed with good coverage moves, but as you can see, Fighting is such a popular coverage move among these Pokemon and many others unlisted and is simply just a common attacking type within OU. Being weak to it is seriously unfortunate. On top of that, the neutrality to the omnipresent Dragon-type attacks significantly reduces opportunities to set up.
This is why I'm still keen on Steel/Ghost. It has literally no offensive potential due to its poor STABs, but can have sufficient sweeping ability after a Belly Drum boost to finish off a weakened team. It's defensive presence, on the other hand, is phenomenal, almost perfect for a Belly Drum user. It's immune to the common Fighting-type hits, meaning it will take ZERO damage upon switching into a Fighting-type attack. This makes Pokemon like Choice Scarf Terrakion and Keldeo potential setup bait. When you don't consider Choice users, Breloom and Lucario are other Fighting-types this CAP can set up against if it was Steel/Ghost since they're coverage moves can't even harm it (Lucario might be running Crunch though). By the way, Steel/Ghost resists all of Terrakion's typical moveset (Close Combat immunity, but Stone Edge/X-Scissor resistance) and even Alakazam running Hidden Power Ice > Hidden Power Fire. What I'm trying to say here is Steel/Ghost provides so many useful resistances and a much-needed immunity against a lot of Pokemon and their moveset, and boasting that resistance to Dragon is a very beautiful thing. Some may argue that Steel/Ghost is too defensive and the player will opt to use it defensively, but this is so easily avoidable it shouldn't be a concern. Kitsunoh was capable of being used defensively because of Will-O-Wisp and Pain Split pretty much. Lucario is a decent example of a Pokemon that boasts a good defensive typing that allows it to set up Swords Dance on a lot of things, but is never used defensively because it doesn't have the movepool or statspread. Something to that effect can be done with this CAP and I feel like Steel/Ghost is the number one type combination that comes closest to ensuring its success.
In order to guarantee setup whilst taking minimal damage in the process, you need high defensive pressure. This can be done fairly easily by having a typing that packs handy resistances and/or immunities and few weaknesses. Steel/Dragon isn't that great when you consider this because it's defensive presence is far inferior to its offensive presence. Sure it packs nifty resistances, but that's mostly due to the part Steel-type. Packing on a Dragon typing makes it take neutral damage from Fire, Ice, and most importantly, Dragon. This keeps it from being able to reliably set up against a potential Salamence locked into Outrage or a Choice Specs Latios's -2 Draco Meteor. You have to consider the most common attacking types out there. I mean, you're taking super effective damage from Fighting-type attacks now, making something like Scizor easily use Superpower rather than the expected Bullet Punch and Breloom or Conkeldurr to nuke you with priority Mach Punch. In fact, the majority of Steel/Dragon's resistances mean nothing when looking at popular Pokemon using said move. For example: it resists Gengar's Shadow Ball, but takes super effective damage from Focus Blast; it resists Terrakion's Stone Edge, but takes super effective damage from Close Combat; it resists Alakazam's Psychic, but takes super effective damage from Focus Blast; it resists Thundurus-T's Thunder and Hurricane, but takes super effective damage from Focus Blast; it resists Hydreigon's Dark Pulse, but will likely take upwards of 50% damage from Draco Meteor due to a neutral hit; it resists Keldeo's Surf, but takes super effective damage from Secret Sword. Also, the Water resistance can be nullified essentially under rain. I mean, you can probably do this with every other typing out there because these Pokemon are typically packed with good coverage moves, but as you can see, Fighting is such a popular coverage move among these Pokemon and many others unlisted and is simply just a common attacking type within OU. Being weak to it is seriously unfortunate. On top of that, the neutrality to the omnipresent Dragon-type attacks significantly reduces opportunities to set up.
This is why I'm still keen on Steel/Ghost. It has literally no offensive potential due to its poor STABs, but can have sufficient sweeping ability after a Belly Drum boost to finish off a weakened team. It's defensive presence, on the other hand, is phenomenal, almost perfect for a Belly Drum user. It's immune to the common Fighting-type hits, meaning it will take ZERO damage upon switching into a Fighting-type attack. This makes Pokemon like Choice Scarf Terrakion and Keldeo potential setup bait. When you don't consider Choice users, Breloom and Lucario are other Fighting-types this CAP can set up against if it was Steel/Ghost since they're coverage moves can't even harm it (Lucario might be running Crunch though). By the way, Steel/Ghost resists all of Terrakion's typical moveset (Close Combat immunity, but Stone Edge/X-Scissor resistance) and even Alakazam running Hidden Power Ice > Hidden Power Fire. What I'm trying to say here is Steel/Ghost provides so many useful resistances and a much-needed immunity against a lot of Pokemon and their moveset, and boasting that resistance to Dragon is a very beautiful thing. Some may argue that Steel/Ghost is too defensive and the player will opt to use it defensively, but this is so easily avoidable it shouldn't be a concern. Kitsunoh was capable of being used defensively because of Will-O-Wisp and Pain Split pretty much. Lucario is a decent example of a Pokemon that boasts a good defensive typing that allows it to set up Swords Dance on a lot of things, but is never used defensively because it doesn't have the movepool or statspread. Something to that effect can be done with this CAP and I feel like Steel/Ghost is the number one type combination that comes closest to ensuring its success.