Snow Warning Kyurem
At first glance one might wonder why we should even bother with hail in Gen 6 now that weather abilities have been nerfed... until you realize that's why.
Let me explain: we have a very small number of hail abusers, Kyurem himself being probably the best one. Magic Guard users, Overcoat users and ice types that don't run Blizzard (like Mamoswine or Cloyster) aren't exactly "abusers", they just don't care.
Keeping this in mind, there are two important consequences about SW Kyurem:
1. we no longer have to worry about opposing weather setters disrupting hail roughly 50% of the time (that was roughly the combined usage of weather teams in BW). Tyranitar is still common, but it will think twice before switching on something that learns Earth Power and Focus Blast.
2. it acts as a weather setter and sweeper rolled into one, much like Kyogre and Mega Charizard Y. Except that now that hail doesn't last forever anymore, this is not a liability for the rest of the team.
This is my favorite suggestion out of the 4 and I see it having a lot of potential.
Refrigerate Avalugg
I'm of the opinion that Avalugg, as it is now, is a terrible spinner but a wonderful physical wall, provided something else provides spin/Defog support. Being able to wall top threats like Garchomp, Dragonite and Mega Pinsir is no small feat. I really hate when people dismiss it because it's an ice type. A pokemon isn't just "a defensive type", it's a combination of type, stats, movepool and ability. Avalugg's titanic physical bulk and access to Recover far outweight its shortcoming as a defensive ice type.
Been said that, Refrigerate would finaly enable it to be a good spinner, who would probably work best in offensive teams who appreciate an unblockable Rapid Spin and would want to keep their own hazards up. Ice is a powerful offensive type and Avalugg's attack is actually pretty good for a wall, so it wouldn't be set-up bait either.
Water Shuriken Cloyster
I don't find this especially helpful to be honest. Cloyster's main issue have always been bulky water types and WS does nothing to fix that. Most steel types in OU have a secondary type that makes them neutral against either Icicle Spear (Ferrothorn, Excadrill, Skarmory) or Rock Blast (Heatran, Scizor). The main steel type who resists both, Aegislash, is actually 2HKO'd by LO Icicle Spear even in its shield form so it's not a surefire counter. WS isn't scoring any notable OHKO against any of them, except for Heatran (who is still OHKO'd by Rock Blast with minimal hazards support anyways). It's probably the least interesting theorymon out of the 4 in my opinion.
Poison Heal Goodra
Goodra is one of those pokemon that have everything a good wall could ask for, except for at the very least a form of semi-reliable recovery. Imagine Gliscor without Poison Heal and Roost, Ferrothorn without Leech Seed or Conkeldurr without Drain Punch. None of them would be even close to their OU status without those tools.
The issue here is that PH on Goodra is just a bit too overpowered. Personally I think Regenerator would have been a better compromise, since it would still make Goodra very viable.
The status immunity is too much in my opinion.