Alright, in order
Sheer Force Kyurem: So this would almost certainly put Kyurem-B down a peg, considering Sheer Force combined with its primarily Special movepool would hit like a truck and the only effective loss would be a drop in Physical power (at most used for maybe a Dragon STAB), Fusion Bolt (might be noteworthy for bulky waters admittedly), and 10 points of defense. Still, the obscene power behind its special movepool (Ice Beam/Blizzard, Earth Power, Flash Cannon, Focus Blast, Psychic, Shadow Ball) and a couple high BP/well typed Physical moves (Outrage, Iron Head) would make this thing a veritable battering ram the likes of Landorus-I. It's main problem as I can pin-point is Dragon Breath being its only Dragon STAB and a need to go mixed to break Fairies and Bulky waters, but neutral targets and common stall options get hit like a truck.
Jellicent + Reflect Type: I might need a bit of elaboration on this one. It's certainly much bulkier than Starmie, who can pull of a similar set to about this effect. However, aside from Toxic Stall or Scald burning I'm not seeing what he'd do with this. Starmie uses it to spin on targets resisting their STABs and mitigate Pursuit trapping. I don't quite see what new jobs this would let Jellicent do, and while it might make him better at some of his walling jobs, I don't know to what degree that would change his niche.
Electric/Steel Flash Cannon Rotom-S: So this thing is pretty much a giant middle finger to every Fairy and Ground type in the tier. This would essentially counter Mega Diancie, non-FB Mega Altaria, Landorus-T, non-HP Fire Latios, Mega Aerodactyl, Diggersby, Mamoswine, Sand Rush Excadrill. Problem is, Rotom-S has significantly less power behind his moves than Rotom-W. But the biggest obstacle it faces for me: he comes with the opportunity cost of not using Rotom-W, who is one of the most splashable glues and Bird Spam checks in the tier, which Rotom-S can't do
252 Atk Talonflame Flare Blitz vs. 248 HP / 252+ Def Rotom-S: 198-234 (65.3 - 77.2%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Mega Pinsir Close Combat vs. 248 HP / 252+ Def Rotom-S: 204-242 (67.3 - 79.8%) -- guaranteed 2HKO after Leftovers recovery
It's an improvement, but his Water counterpart just brings so much more to a team that I'm not sure what he'd contribute specifically to these teams.
Quiver Dance Galvantula: Pretty neat improvement, main competition in Volcarona. Less SR weak and faster naturally in exchange for lesser bulk. Lack of Fire STAB is disappointing, and a bit of coverage trouble, but seems interesting. I'll need to see more of this.