Deck Knight
Blast Off At The Speed Of Light! That's Right!
I'll cover a bit about each of the types brught up in Elite Lord Sigma's post.
Ice/Fighting: My gut reaction to this is "no, hell no." I don't know quite why I feel that strongly, but a few key points:
Ice is a horrible type for any kind of pivot. It's weak to SR and two kinds of priority, and only resists itself. Even if you mitigate some of its weaknesses with a better defensive Sub-type like Water, Steel, or Dragon there's no getting around just how bad Ice-type Pokemon of any stripe are at pivoting in and out. Ice/Fighting does neutralize the SR weakness, but it's still weak to 3 common and powerful types of priority in Brave Bird, Bullet Punch, and Mach Punch. The typing is also walled by Azumarill (save for Freeze-Dry), and although it isn't weak to Aqua Jet it's still another threat to watch out for.
I think the key problem for it compared to say Fairy/Fighting is that while they are threatened by similar things (Kitsunoh, Mollux, Mega Metagross & friends), Ice/Fighting has so many weaknesses it really doesn't draw in specific threats, and the kind of threats it draws (and the pokemon that might stay in on it) have more options against it. Scarf Heatran threatens both types, but you *know* it's going to select Flash Cannon on Fairy/Fighting whereas it can opt for either Flash Cannon or Fire Blast on Ice/Fighting CAP. Tomohawk can click either Hurricane/Air Slash or Aura Sphere on Ice/Fighting, it always picks flying STAB against Fairy/Fighting. Problems like this make it much more difficult to either Parting Shot (if CAP is also Scarfed) or switch to an appropriate counterswitch to eat the resisted hit.
Electric/Grass: This one is interesting and potentially pretty cool. Compared to other discussed types being total Talonflame or Zard bait, this one exchanges issues with ZardX after it Megas with scaring off Talonflame and ZardY. One particularly prominent weakness of it, though, is that it's weak to U-turn and therefore will attract a lot of Pokemon very willing to just throw U-turn out to both prevent it from switching in and negate the status drops of Parting Shot, at least for their own switchin. There are of course viable avenues that make throwing around U-turn (unless you're Scizor or Syclant and wiping out your target at the same time) extremely undesirable, and CAP's STAB on Electric makes a lot of the good U-turners hesistant to try and just outmaneuver it with that.
I think some decisions would need to be made down the line on how to mitigate the U-turn weakness, but Electric/Grass CAP would be perfectly viable against other things it doesn't address so well like Knock Off/Pursuit in the course of making those decisions.
Ice/Fighting: My gut reaction to this is "no, hell no." I don't know quite why I feel that strongly, but a few key points:
Ice is a horrible type for any kind of pivot. It's weak to SR and two kinds of priority, and only resists itself. Even if you mitigate some of its weaknesses with a better defensive Sub-type like Water, Steel, or Dragon there's no getting around just how bad Ice-type Pokemon of any stripe are at pivoting in and out. Ice/Fighting does neutralize the SR weakness, but it's still weak to 3 common and powerful types of priority in Brave Bird, Bullet Punch, and Mach Punch. The typing is also walled by Azumarill (save for Freeze-Dry), and although it isn't weak to Aqua Jet it's still another threat to watch out for.
I think the key problem for it compared to say Fairy/Fighting is that while they are threatened by similar things (Kitsunoh, Mollux, Mega Metagross & friends), Ice/Fighting has so many weaknesses it really doesn't draw in specific threats, and the kind of threats it draws (and the pokemon that might stay in on it) have more options against it. Scarf Heatran threatens both types, but you *know* it's going to select Flash Cannon on Fairy/Fighting whereas it can opt for either Flash Cannon or Fire Blast on Ice/Fighting CAP. Tomohawk can click either Hurricane/Air Slash or Aura Sphere on Ice/Fighting, it always picks flying STAB against Fairy/Fighting. Problems like this make it much more difficult to either Parting Shot (if CAP is also Scarfed) or switch to an appropriate counterswitch to eat the resisted hit.
Electric/Grass: This one is interesting and potentially pretty cool. Compared to other discussed types being total Talonflame or Zard bait, this one exchanges issues with ZardX after it Megas with scaring off Talonflame and ZardY. One particularly prominent weakness of it, though, is that it's weak to U-turn and therefore will attract a lot of Pokemon very willing to just throw U-turn out to both prevent it from switching in and negate the status drops of Parting Shot, at least for their own switchin. There are of course viable avenues that make throwing around U-turn (unless you're Scizor or Syclant and wiping out your target at the same time) extremely undesirable, and CAP's STAB on Electric makes a lot of the good U-turners hesistant to try and just outmaneuver it with that.
I think some decisions would need to be made down the line on how to mitigate the U-turn weakness, but Electric/Grass CAP would be perfectly viable against other things it doesn't address so well like Knock Off/Pursuit in the course of making those decisions.