Glad this thread is alive, thanks Shadestep :)
Recover Claydol, Stays B
This would not make defensive claydol viable, maybe to an extent it could run rapid spin, rocks, recover and psychic but it's poor defensive typing just makes it pretty pathetic, and not to forget, pursuit bait. Even on a niche offensive set it would still serve no use being a waste of a moveslot on a pokemon that already has a severe case of four moveslot syndrome it just isn't worth it.
Rapid Spin Carracosta, B --> A-
Ok, so Rapid Spin Costa actually sounds pretty cool, it would be an incredibly bulky spinner that can easily get a free spin of mons like tauros, archeops, etc. It has that great ability to switch in and not lose 25% of its health like a pleb mon *cough mantine cough*. It doesn't lose much moveset wise since it can run rocks, rapid spin, scald, filler. The only problem might be that it suffers the samd way Claydol does as in, by using it as both your stealth rocker and spinner it builds too much pressure on that specific mon however unlike Claydol, Carracosta has respectable bulk so it's not as big of an issue.
Dragon Tail Sliggoo B --> A-/A
Ok before I talk about Dragon tail I wanna talk about normal sliggoo, it acts as a brilliant spdef wall, meanwhile it acts as a decent late game win con. However the standard set -which consists of rest, sleeptalk, curse, outrage- has two main problems, the first is it's easily set up on by things like scyther, rhydon, malamar and more, and two is that it has to be asleep before it can attack because locking yourself into outrage prematurely is a death wish.
Dragon tail solves both of these, it stops the things I previously mentioned from setting up, while also allowing it to hit something without locking yourself into an easily exploitable move. I believe this would allow it to rise in viability incredibly simply because it sets up on so much, and with dragon tail, prevents anything that might wanna stop it.
Ice Beam Rotom-Frost, C- --> C+
Ice Beam on rotom-f would allow its viability to grow quite a bit. It seperates its self from pokemom like lapras, vanilluxe, jynx, articuno and aurorus by having volt switch. The problem with blizzard was its just so unreliable and forced the user to click volt switch more often than not because of the fear of wasting a turn. By giving it ice beam it doesn't require a hail setter or wide lens and has better options like specs, lo or scarf. It still has some glaring flaws but it instantly would become more viable with beam.