Hmm... a bit like my own Team Green, only more restricted
Okay...
The pick of your availables are:
Milotic
Blissey
Gorebyss
Mr.Mime
Wigglytuff
Clefable
Lickitung
with useful backup from
Delcatty
Corsola
Porygon
Flaafy
Exeggcute
Forget the babies and Hoppip.
Main problem, which is not overly serious, is too many Normals. This could suggest a vulnerability to Fighting, but since you're well served with Psychic, is probably not too bad. Due to the limited types available, I'd say Milotic, Mr.Mime and Gorebyss are essential. Blissey is in a class of its own. Lickitung, Clefable and Wigglytuff are pretty much variations on a theme. Porygon or Flaafy probably give you the best type coverage among the 2nd stage ones. I'd tend to avoid Delcatty in a team likely to already include Blissey, Wigglytuff, Clefable or Lickitung - besides it's more purple than pink.
One that you haven't got on your list is Ditto... the pinkest one of all! It could add just the right amount of unexpected coverage you need.
Provisionally, I'll suggest these:
Milotic (Calm/Modest)
Surf
Recover
Ice Beam
Mirror Coat/Confuse Ray/Attract/Double Team
Mr.Mime (Modest)
Substitute/Reflect
Baton Pass/Light Screen
Psychic
Magical Leaf
Gorebyss (Bold)
Whirlpool/Baton Pass
Amnesia
Ice Beam
Surf/Water Pulse
Blissey (Modest/Quiet)
Counter
Substitute
Rest
Psychic
Wigglytuff (Adamant)
Shadow Ball
Double Edge
Rollout/Brick Break
Rest
Ditto (Timid/Jolly)
Transform
Wigglytuff is your best bet for physical attacker - Double Edge with STAB is not to be sneezed at. It also has a good choice of physical attacks. Mr.Mime can Baton Pass a Sub *or* be trained to pseudopass - all are level up moves so you can change them easily to see what works the best. It's also a solid special sweeper - and gives you a Grass move that is handy. I'd suggest him as the Starter since his non-attack moves work best in that position. Gorebyss can trap something that can't hurt it badly with Whirlpool then tank up with Amnesia. Milotic is just plain good. It starts out effectively tanked since only Grass and Electric are supereffective against it, and it has a massive special defense. Recover makes it very durable, and it can otherwise just dish out the damage. You may consider it too similar to Gorebyss, but two pure water types on a team of 6 isn't a major problem when nothing else is vulnerable to Grass or Electric. The Fighting weakness is more of an issue, but Mr.Mime and Blissey should be OK to cover them with Psychic and Counter. Because the five team is strong, Ditto should be OK to add surprise value and type coverage. I suggested a +speed personality to improve the chances that he'll end up faster than the pokémon he's copying.