Veedrock has a good point, since a perma-weather abuser would not be the greatest idea (in case this sounds hypocritical on my part, I didn't suggest that my Sun Abuser concept would have Drought). A minor nitpick would be that Rain teams carry at leat one Pokemon with a Damp Rock, so Kingdra would have a little longer to sweep. If "Kingdra in the Snow" passes anyway, we could limit its movepool significantly to make it managable (bulky Waters sans Swampert can manage fine against Kingdra, for example, since it relies on two Water moves and typically Draco Meteor for the Rain variety).
Guys, don't forget one thing: no matter what ability you can give to CAP8, he will never be Kingdra.
What I mean is, he will never have all the advantages Kingdra has. First of all, while Ice hits more things supereffective than Water, it offers lesser neutral coverage. With things like Scizor, Tyranitar and especially Heatran lurking around, spamming Blizzard is nowhere as effective as spamming Surf.
Moreover, Blizzard is not powered up like Surf is, so it will do less damage (120BP+STAB vs 95BP+STAB+Rain Boost). If you add that Blizzard has only 8PP, you see that it is less powerful.
But most importantly, there is no "icy" Waterfall. What I mean is, no matter how powerful your Blizzard is, Blissey and friends can sponge it without much problem, even if it comes from the likes of Glaceon.
Finally, while there's no perma rain, Tyranitar can come much more easily on an Hail team rather than a Rain team. And while a Rain team generally has 2 or 3 setuppers, Hail teams only have Abomasnow.
EDIT:And don't forget how better Water is defensively than Ice. What makes Kingdra so threatening is his lack of weaknesses and, most notably, his resistance to the ubiquitous Bullet Punch. An Ice type, on the contrary, would be
weak to Bullet Punch, or at best neutral. And while you should say, "just pack Magnezone", you still have to fight with a fighting weakness (no pun intended). And there's no type resistant to both Steel and Fighting, so, if CAP8 don't want to give up the Ice STAB (ending being not even comparable to Kingdra in terms of threat, even if still good), you will always be weak to either Bullet Punch or Mach Punch/Vacuum Wave.
So, both offensive teams and defensive ones will probably have an answer to CAP8 (respectively, priority revenge killing/resistance switching and standard special sponging)