I have to fervently disagree with the opinion that more ice types = bad hail team. 3 Ice types is perfectly viable in UU.
Simply put, both Hail Stall and Hail Offense work a lot better with the ice types, both because of the recovery and the STAB Blizzard. Hail Stall can run (I'll post an RMT up sometime) Walrein, Froslass, and Snover without any significant single weakness (though Fire is a problem, but Blastoise alleviates that problem somewhat). Offense can go Rotom-F, Glaceon, and Snover, which is significantly less synergistically solid, but so are Triple-Fire and Double-Dragon strategies, neither of which are allowed to have a 120BP STAB 100% accuracy move without drawbacks (Outrage, Flare Blitz, anyone?). It's true that Ice is a horrible typing to begin with, but that's only defensively.
The presence of hail also allows the use of some very unique combinations for Ice-types, such as Stallrein (duh) but also unique stuff such as Ice Body Choice Specs/Life Orb Glaceon, which loses only 4% through LO recoils or can effectively run both Lefties and Specs simultaneously (though Specs is always better, imo). Hail also neutralizes recovery on opposing Pokemon and allows for closer 2hkos and 3hkos.
Overloading on Blizzspammers is an underrated idea, but let's throw in some calculations:
252+ SpA Choice Specs Glaceon Blizzard vs. 252 HP / 4 SpD Blastoise: 42.54 - 50.27%
2hko in Hail + Any form of Entry Hazard
252+ SpA Choice Specs Glaceon Blizzard vs. 252 HP / 4 SpD Suicune: 35.39 - 41.58%
SOLID 3hko against Suicune, becomes a handy 2hko after a couple layers of spikes, which come courtesy of Froslass
252+ SpA Choice Specs Glaceon Blizzard vs. 252 HP / 252+ SpD Umbreon: 49.49 - 58.12%
Premier UU Special Wall, taken down in 2 hits without any sort of hazards.
252+ SpA Choice Specs Glaceon Blizzard vs. 252 HP / 80 SpD Eviolite Porygon2: 55.34 - 65.24%
One of the bulkiest Pokemon in UU, and Glaceon outspeeds.
and I think that's the strongest spammer, though Rotom-F has more options as LO Subsplit or Choice Scarf. It fails to 2hko Umbreon, but anything that gets hit neutrally will be dead after another Blizzard, generally speaking.
It's true that there are Pokemon that ruin hail, such as Heracross, but it should be possible to dance around them especially when hazards are up.
One more caveat, which is amazing for hail stall:
For grounded Pokemon (even SR resist) with 3 layers of Spikes, 1 layer of TSpikes and SR, minimum entry damage is 6.25%(resists SR)+25%(Spikes)+6.25%(Hail)+12.5%(Poison) which is literally 50% of health per switch in. Neutral to SR takes more, obviously, and Steel types are the exception to poison. Stuff like Roserade and Nidoqueen can absorb TSpikes but both are obviously weak to Blizzard, meaning that not even the gutsiest player will feel comfortable bringing either Pokemon in. Flying types don't take Spikes but are equally vulnerable to Blizzard.