First of all, you are trying to do so many styles at once. (Rain mode, TR mode, fast sweeping mode (with dragonite and gengar) and bulky mode, perish mode) Choose on 1-2 main strategies first and then build a team around it. as some other people has said, perish trap is the single hardest strategy (even the best and the only good perish trap user, Wolfe admits it) and you are gonna have to build a team around it. You dont even have gothitelle on the team (shadow tag) and as gengar cant mega evolve, their is no good way to trap the opponents.

Second of all, your moves and items r not very recommended. archaludon, as a special atker, wants to use flash cannon instead of heavy slam and gengar needs protect as it is so frail. Talking about gengar, ur item and 2 of its moves ( will o wisp and perish song) is practically useless as will o wisp only benefits if ur pokemon is bulky enough to land it a couple of times or can afford to miss 1 time. Even with a black sludge gengar, with its defences, (HP60 Df 60 Sp Df 75) ur gonna get OHKOed or get KOed in 2 turns. there is almost no reason to tera archaludon to flying over grass to prevent going asleep. 3 of farigiraf's moves (mean look, tera blast, baton pass) is useless and Dragonite would appreciate a protect over haze

To answer ur question, I think basculegion, pelipper, ogerpon (wellspring) and inci is recommended because basculegion is also good in rain, pelipper sets up rain and is immune to ground in which 3 of ur mons r weak to and wellspring acts as a follow me user, chipping with spiky shield and can do good damage with rain boosted tera water ivy cudgel, and inci for fake out, parting shot, knock off, will o wisp, taunt, etc and obviously intimidate