What should my 6th Pokémon be? [Nuzlocke, Fire Red]?

I am doing my first Nuzlocke challenge for the ROM hack, Omega Fire Red [Please don't spoil anything for me ;) ]. I have been training for the elite 4 and I'm assuming they'll be in the Lv 70 - 80 range for the first time around.

The 5 Pokémon I currently have with approx EVs:

Kingdra [240HP, 252 SpA,16 Spe] [Rain Dance, Surf, Ice Beam]

Forretress [252HP, 252 SpD] [Spikes, Rapid Spin, Toxic]

Starmie [252SpA, 252 Spe] [Surf, Psychic, Ice Beam, Thunderbolt]

Mr Mime [252HP, 80SpA, 10 SpD, 166 Spe] [Calm Mind, Baton Pass, Psychic, Encore/Subsitute]

Gyarados [100HP, 252 Att, 156 Spe] [Dragon Dance, Earthquake]

I am able to get evolutions that normally need to be traded, but cannot get extra items/tms.

I plan to give Calm Mind to Mr Mime to make him a baton passer.

I have already used Psychic on Starmie.

I plan to give Rain Dance to Kingdra.

I plan to give Earthquake to Gyarados.

I plan to give Toxic to Forretress.

I'm considering to give Substitute to Mr Mime unless I'm giving it to a SubPuncher.

Any breed moves are out of the question for this challenge.

What would you recommend from this list? [All at 0 EVs]

Jumpluff

Lunatone

Clefable

Dewgong

Smeargle

Raichu

Magneton

Ninetails

Rapidash

Arcanine

Miltank

Tentacruel

Gengar

Walrein

Crobat

Weezing

Victreebell

Sunflora

Seaking

Granbull

Dodrio

Xatu

Golduck

Gorebyss/Huntail [This is a 50/50 on what it would evolve into.]

I'm thinking of grabbing Smeargle for a small Baton Pass chain, but he's fragile...

What's your recommendation?