Thanks! Dugdrio or garchomp might be a good contender. I don't like his firefang getting reduced, but at least he can function outside of rain. I'm trying to go without hazards, because I have pelipper as a defogger, and hazards are everywhere now thanks to toxapex.A-Raichu has been confirmed to be pretty bad and redundant in the metagame, Kingdra is still the prime special sweeper for Rain Teams. Mega-Scizor is a nice addition because Rain reduces its fire weakness, and it forms a solid VoltTurn Core with Koko. Dugtrio is also a nice option on those kind of teams, because with 2-3 U-Turns or Volt Switches in the team already, you can almost always safely bring it in, and it also acts as an Electric resist.
Garchomp is often used as another Elec resist over the likes of Duggy, and also a good rocks lead. Other options that are commonly seen on rain teams are: Tornadus-T (u-turn, 100% acc Hurricane in rain, complements pelipper for a defensive core), Latias (ele resist, 100% acc thunder in rain, Healing Wish), Kabutops (best physical swift swimmer in combination with kingdra), Ferrothorn (hazards, beats bulky water, fire weakness reduced), or Mamoswine as a Lead.
Edit: A-Marowak is also really nice, but remember his Fire Stab gets reduced in Rain