Wubben, apologies for a delayed response, but
here is our best attempt to build around Rapid Spin Starmie.
We did edit the set a bit; without a Life Orb, Analytic, and max Special Attack investment, Starmie will simply not do any damage with Hydro Pump and Thunderbolt. For this reason we adopted a moveset better suited for a utility Pokemon in Scald and Toxic.
We started the building process with Guzzlord, as it grants a resistance to Dark, Ghost, Electric, and Grass for Starmie and also checks all spinblockers for Starmie.
Garbodor sporting a Rocky Helmet to punish U-turn spam. Spikes paired with Guzzlord's Dragon Tail pair very well together, accruing a large amount of damage even from a defensive core.
Silvally-Ground provides some offensive pressure for the team, an Electric immunity, and it benefits greatly from Garbodor's Spikes, especially when it can force in checks and U-Turn out while they get damaged by Spikes.
Diancie provides some good type resistances, but most importantly provides Stealth Rock and Heal Bell in one slot. Diancie is an effective check to some breakers such as Exploud or Goodra.
Choice Scarf Rotom-Mow wraps up the speed control needs on an otherwise slow team. TrickScarf with Nasty Plot is freed up over Defog because Starmie has Rapid Spin, meaning Rotom-Mow can destroy very bulky teams in match-ups where it doesn't need a Choice Scarf.
This team is fairly weak to Goodra (what team isn't) so you may have to do some creative pivoting around it. The Starmie set was quite difficult to build around, as most teams typically don't
start with a utility hazard remover, so it was a challenge to make, and we hope you enjoy it.