>>47919170For abilities, Ludicolo would gain Drizzle (Replacing Swift Swim or Rain Dish, take your pick) so it can set up rain instead of relying on other mons for rain.
Something a little more out there would be replacing Own Tempo with Dancer as its HA.
More dance moves would be nice for Ludicolo to have access to. Petal Dance and Quiver Dance in particular would be very useful additions to Ludicolo's movepool.
I'm not sure if I want to give Ludicolo more healing, since it already has Giga Drain and Rain Dish, but for the hell of it, here's a new move since Synthesis isn't a reliable healing option in the rain.
Irrigation is a Water-type move that heals the the user by half of its max HP with no weather, two-thirds HP in rain, and one quarter in all other weather. Essentially a rain version of Synthesis.
I think these buffs are enough to make Ludicolo pretty viable, so I'm going to lay off on stat buffs. Perhaps a small boost in HP and Speed, but I'll leave it there.