that is one of the best teams i've seen so far in my life!!!!
i would give something with a massive base attack like a
obviously havent seen many teams.
first off, evovle the pikachu and get rid of the legendary.
then you are looking at:
Rachu (go surfing so he is a special sweeper)
add rhyperior because it has stats on par with legendaries and has the solid rock ability which is amazing.
then you got:
i would then add a special sweeper. you already have 3 physical guys with rhyperior, snorlax and slowking functioning as walls/ slow speepers.
maybe a yanmega, gardnevoir, alakazam, porygon z or gengar?
since you want speed i would do:
yanmega ( gardnevoir, alakazam and gengar would share a dark type weakness with slowking and porygon z is too slow)
thats pro. almost as pro as my baton passing to ramphardos set. never lost a wifi battle with it
(if you steal my idea above just give me credit please