I love the idea of Momento on Uxie, and will use HP {Ground} over {Fire} on Galvantula.
As for a rapid spinner; I rather like the set you provided of:
-Stealth Rock
-Rapid Spin
-Waterfall
-Toxic
Nature: Impish
EVs: 252 HP/72 Def/184 Spe
Item: Leftovers
Ability: Swift Swim
But with Stealth Rock already on the field (although the extra security in case of an opposing Rapid Spin is quite useful) couldn't Protect be used as a form of recovery with Leftovers and aid in the Toxic damage?
This seems tempting, but it seems like you're going to forgo Waterfall completely; doing so will render Kabutops susceptible to Taunt, meaning that if it gets Taunted, it'll be forced to attack with Rapid Spin, which is a rather weak move by itself. The reason why Waterfall is on Kabutops is so it won't be Taunt bait.