Im still going to go strong with Larvitar. RP Tars only weakness is priority, and the most common priority mon that can KO it quite easily is Croagunk. Croagunk manages piss against Wynaut, as Wynaut can encore Sucker Punches and Encore Counter Coat its other attacks.
Wynaut here can easily take out Gunk, then encore some electric move ( Elekid or Mantyke with HP Electric are okay choices) or set up moves and just go to Larvitar. RP up, Guts activate, and proceed to sweep.
I agree that this is coulping up on Ice Weakness, but atleast Dratini can be a go to guy for water moves.
As for the potential teammates, I think we could effectivley use a Hazard Lead, like maybe Anti-lead omanyte but with Spikes > SR and a general annoyer which can phaze. I think this would greatly beenfit us as a) this team is about giving sweepers a free set up turn. Our sweepers are suchthat one set up turn can possibly result in a loss for the opponent straight away. This way we can use the other team slots for support such as hazards and phazers. Another reason is that we often see stuff just missing out on the KO. with Spikes and SR this can often be turned into an OHKO.
For the support phazer Id like to suggest Slowpoke . With a moveset of T-Wave / Yawn / Waterfall and ZButt or Return, SLowpoke is a general annoyance for nearly every physical threat. Paralysis is extremely helpful if you can paralyse a scarfer, as then DDTar can be viable due to there being nothing faster then it or tieing with it. Yawn might seem counter productive with TWave, but consider the fact that when you Yawn, your opponent can either stay in and get slept, allowing for a free switch in, or switch out and make the next mon take entry hazard damage. Slowpoke could potentially go Yawn -> Yawn to catch the next mon on the switch. The Vital Spiritful Mankey can do jack shit against Slowpoke. Slowpoke can also run Slack Off over Waterfall or Zen Headbutt for recvoery, but I doubt that it would need it that often.
Other mons that come to mind here in the case of status spreading are Double Powder Paras , who can Spore and follow up with Stun Spore to cripple two Pokemon straight off the bat, and possibly a Venonat lead with Agility / Sleep Powder / Stun Spore / Baton Pass. I say Venonat as a lead because potentially, if you have a member of the team slept, another one paralysed, you can simply just pass the Agility to Larvitar and start sweeping at the start of the match. Dratini can perform an easy clean up later on
tl;dr:
Team can use Hazards and Phazing
Omanyte / Venonat are possible leads
Slowpoke is a possible general support mon
Larvitar is the pokemon with the highest average between badass and outright cute