All out LO attacking set has merit, but i'm still interested in a slightly more niche / utility set that distinguishes itself from an all out attacking set.
thunderbolt / u-turn / roost or natures madness / taunt or natures madness
w/ Zap plate
Now, before you say this set lacks power, let me clarify, it doesn't
252 SpA Zap Plate Dedenne Thunderbolt vs. 0 HP / 0 SpD Mega Medicham in Electric Terrain: 246-289 (94.2 - 110.7%) -- guaranteed OHKO after Stealth Rock
---> in comparison, with just a Zap plate, it outpowers LO thundurus:
252 SpA Life Orb Thundurus Thunderbolt vs. 0 HP / 0 SpD Mega Medicham: 214-253 (81.9 - 96.9%) -- 25% chance to OHKO after Stealth Rock
more calcs:
252 SpA Zap Plate Dedenne Thunderbolt vs. 0 HP / 0 SpD Weavile in Electric Terrain: 246-289 (87.5 - 102.8%) -- guaranteed OHKO after Stealth Rock
252 SpA Zap Plate Dedenne Thunderbolt vs. 0 HP / 0 SpD Bisharp in Electric Terrain: 286-337 (105.5 - 124.3%) -- guaranteed OHKO
252 SpA Zap Plate Dedenne Thunderbolt vs. 0 HP / 0- SpD Mega Diancie in Electric Terrain: 219-258 (90.8 - 107%) -- guaranteed OHKO after Stealth Rock
252 SpA Zap Plate Dedenne Thunderbolt vs. 248 HP / 0 SpD Rotom-W in Electric Terrain: 202-238 (66.6 - 78.5%) -- guaranteed 2HKO after Leftovers recovery
252 SpA Zap Plate Dedenne Thunderbolt vs. 252 HP / 84+ SpD Clefable in Electric Terrain: 195-229 (49.4 - 58.1%) -- 64.5% chance to 2HKO after Leftovers recovery --> though if you runt taunt, its definitely able to take out Clefable.
The raw power of electric terrain thunderbolt, even with zap plate over life orb, is insane. There is no need to run LO and make a mon with good resists and usable defences lose 10% of its hp every turn.
Now with its bulk not being compromised, Tapu KoKo reliably checks quite a few mons, and, since it only really needs to outspeed weavile in OU, there are 40 spare evs for hp:
252 SpA Life Orb Latios Psyshock vs. 40 HP / 0 Def Dedenne: 196-231 (67.3 - 79.3%) -- guaranteed 2HKO
252 Atk Life Orb Bisharp Sucker Punch vs. 40 HP / 0 Def Dedenne: 82-97 (28.1 - 33.3%) -- 0% chance to 3HKO (taking into account sucker punches new 70 base power)
252 Atk Aerilate Mega Pinsir Return vs. 40 HP / 0 Def Dedenne: 141-167 (48.4 - 57.3%) -- 94.1% chance to 2HKO
also survives:
+2 44 Atk Technician Mega Scizor Bullet Punch vs. 40 HP / 0 Def Dedenne: 217-256 (74.5 - 87.9%) -- guaranteed 2HKO
and can hit back with:
252 SpA Zap Plate Dedenne Thunderbolt vs. 248 HP / 200 SpD Mega Scizor in Electric Terrain: 177-208 (51.6 - 60.6%) -- guaranteed 2HKO
which is a lot of damage.
Natures madness + taunt is there for mons like amoongus and chansey. I personally prefer the idea of taunt / roost, as koko can taunt and roost on fat mons, then u-turn out. Though natures madness certainly has its use. U-turn was chosen over volt switch as pokemon like hippodown and landorus-t would otherwise be too damaging to this team and would suck too much momentum - which is what this set is ment to grab. U-turn also is good as when latios switches in on a thunderbolt, if rocks are up, u-turn has a chance to KO after a thunderbolt (even with timid and no evs).
Overall, an all out attacking set certainly has promise, and will probably be the set mainly used, but a slightly more niche set that offers utility and longevity certainly is enough to make a set like this still relevant in OU.