Rain Team for an Alpha Sapphire playthrough

Approaching gym 7 in my run and therefore story climax. At this point i started to planning for my elite 4 team, while realising i never used rain team before and super exited to do so, team building and planning are my favourite parts of a game. However i don't have much experience, thus i require advises.

My current plan:

Kyogre, Drizzle, rain set-upper obviously

Swampert, Swift Swim during mega, STAB earth moves

Ludicolo, Swift Swim or Rain Dish, which one is better, STAB grass

Tentacruel, Rain Dish, probably would have to use instead of Kingdra, STAB poison moves

Manectric, for STAB Thunder

Armaldo, Swift Swim, just for more coverage

To be considered:

Peliper, Rain Dish, STAB Hurricane

Kingdra, Swift Swimm, assuming it's easy to find someone ho will trade me a Horsea with dragon scale or at least trade mine back

Parasect, Dry Skin, hard to acquire

Golduck, Swift Swim

Huntail, Swift Swim, requires trading

Castform, Forecast, Weather Ball

Dewgong, Hydration, STAB ice moves, hard to acquire

Whiscash, Hydration, STAB earth moves

Gorebyss, Hydration and Swift Swim, requires trading

Alomomola, Hydration

Vaporeon, Hydration, hard to acquire

Seismitoad, Swift Swim, STAB earth, hard to acquire

Luvdisc, Hydration and Swift Swim, Trash anuway

Carracosta, Swift Swim, hard to acquire

Beartic, Swift Swim, STAB ice, hard to acquire

Any electric type for Thunder, though i doubt anything would be better than Manectric due to it's ability to mega, only Lantern and Magnezone probably, for their Typing

Could also bring something from gen 5 or 6 games thorough Pokemon Bank and Poke transfer, though it will kinda ruin game integrity for me

Also i have no idea what items should i use apart from mega stones