I'd say that the problem with your post is that you are thinking about countering a whole bunch of stuff... but all at once. With Electric/ Water every set will be Electric/ Water/ Ice/ Coverage which destroys the point of having such a pokemon. Why not use Suicune?There are two things I would like to suggest:
1: Mono-Electric. Electric already is good in terms of lack of weaknesses, and adding any other type, especially one to sponge Earthquakes, will give Electric more weaknesses than it's worth. It's not worth tradeing a Earthquake weakness to a Weakness to Rock, and Ice, or Fire, and Ice, or Rock and Fire. If CAP10 is faster than your common Earthquaker, then, it probobly won't be losing.
2: Electric/Water:
I was on the fence for Electric or Water, and while this might sound like a beefed up Lanturn... OK, maybe that's what it'll end up as. Let's face it, a lot of common Earthquakers dislike either Water, Electric, or the Ice Beam that 99% of water types automatically get.
Off the top of my Head:
Tyranitar: Hit SE by Water attacks, probobly will be slower than CAP10
Gyarados: Thunderbolt
Salamance: Ice Beam [Provided we get it]
Heatran [Earth Power]: Water move
Flygon: This one will probobly outspeed CAP10, but can fall on the switch-in to an Ice Beam
Gliscor: Ice Beam/Water Move
Metagross: Depends on CAP 10's stats if it could switch in or not
Swampert: Will probobly end up as the counter to an Electric/Water CAP 10.
So, aside from defeating most common Earthquake users, we gain a weakness to Grass [Not common] and Electric [Canceled], but gain resists to Fire, Ice, and Water, ALL very common attacking types.
Keeping EQ weakness, being able to discourage common EQ'ers, and gaining 3 useful resists > Being weak/immune to EQ, and gaining even more harmful weaknesses
I'm suggesting Electric/ Poison. Giving this thing two good STAB moves just means that it will be running them all the time, and every pokemon needs a downfall less it become broken. Even if we are dooming it to a four times weakness there is still Magnet Rise and Levitate to mediate those. Poison's useful Toxic and Toxic Spike immunity are a key aspects to succeeding. Getting Toxic Poisoned on the switch cripples CAP10 before it's even had a chance.
I also like Electric/ Flying and I want to see how we can differentiate it from Zapdos. It's a great typing, only being weak to Ice and Rock, though the 25% hit on the switch is a bit daunting, Flying eliminates the Ground weakness and gives CAP10 immunity to Spikes and Toxic Spikes. Flying is also an lesser used attacking type, which ensures that not every CAP10 will be running Dual STAB/Coverage. What Zapdos carries Flying moves?