Most likely refers to how the team has all Gen I Pokemon in it.
Stealth Rock is a staple entry hazard to use in competitive play. IMO, Clefable should be the one to set it up:
-Stealth Rock
-Moonblast
-Fire Blast/Thunder Wave
-Soft-Boiled
Nature: Calm
EVs: 252 HP/172 Def/84 SDef
Item: Leftovers
Ability: Magic Guard
Arcanine may have a small niche as an offensive and defensive Fire Pokemon, but I think Charizard should be the Mega to use, as it has better power, Speed, and defensive typing. However, this means replacing Blastoise with Starmie; while the latter is weaker than Blastoise, it's faster and has just as good coverage:
Charizard:
-Dragon Dance
-Flare Blitz
-Dragon Claw
-Earthquake/Roost
Nature: Jolly/Adamant
EVs: 252 Atk/4 Def/252 Spe or 104 HP/220 Atk/184 Spe
Item: Charizardite X
Ability: Blaze
or
-Flare Blitz
-Dragon Claw/Earthquake
-Will-o-Wisp
-Roost
Nature: Adamant
EVs: 248 HP/24 Atk/180 SDef/56 Spe
Item: Charizardite X
Ability: Blaze
or
-Swords Dance
-Tailwind
-Flare Blitz
-Outrage
Nature: Adamant
EVs: 40 HP/252 Atk/216 Spe
Item: Charizardite X
Ability: Blaze
Starmie:
-Hydro Pump
-Psyshock/Ice Beam
-Thunderbolt/Hidden Power (Fire)
-Rapid Spin
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Ability: Natural Cure/Analytic
or
-Scald
-Psyshock/Reflect Type
-Rapid Spin
-Recover
Nature: Timid
EVs: 252 HP/4 SAtk/252 Spe
Item: Leftovers
Ability: Natural Cure
If you want to keep Arcanine and Blastoise, use Wild Charge over Thunder Fang for the former. The recoil is worth the extra power:
252+ Atk Life Orb Arcanine Thunder Fang vs. 4 HP / 0 Def Starmie: 205-244 (78.2 - 93.1%) -- guaranteed 2HKO
252+ Atk Life Orb Arcanine Wild Charge vs. 4 HP / 0 Def Starmie: 286-338 (109.1 - 129%) -- guaranteed OHKO
(of course, Arcanine has to hit Starmie on the switch, as Starmie outspeeds it otherwise)
252+ Atk Life Orb Arcanine Thunder Fang vs. 252 HP / 232+ Def Slowbro: 125-148 (31.7 - 37.5%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Life Orb Arcanine Wild Charge vs. 252 HP / 232+ Def Slowbro: 172-203 (43.6 - 51.5%) -- 99.6% chance to 2HKO after Stealth Rock
Weakness Policy is matchup-dependent. It's true that it punishes opponents who hit Dragonite with a super effective attack while Multiscale is active, but it's not worth it because Dragonite is prone to being crippled by burn or paralysis without a Lum Berry. Extreme Speed is also a must, IMO, since it provides useful +2 priority:
-Dragon Dance
-Outrage
-Earthquake/Fire Punch
-Extreme Speed
Nature: Adamant
EVs: 252 Atk/4 Def/252 Spe
Item: Lum Berry
Ability: Multiscale
Snorlax makes the best use out of Assault Vest, as it has good coverage and appreciates the extra special bulk:
-Return/Body Slam
-Earthquake
-Pursuit/Crunch
-Fire Punch/Crunch
Nature: Adamant
EVs: 252 Atk/252 SDef/4 Spe
Item: Assault Vest
Ability: Thick Fat
While Hypnosis is a sleep move, it's rather inaccurate. Gengar may not seem like a utility attacker from its stats, but it can force switches easily, as it has a good defensive typing + Levitate. If you must use a coverage move, Focus Blast, despite the shaky accuracy, is preferred, as it lets Gengar hit Steels harder than Shadow Ball would:
-Shadow Ball
-Sludge Bomb/Sludge Wave
-Focus Blast
-Taunt/Destiny Bond/Icy Wind/Substitute
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Black Sludge/Focus Sash
or
-Hex
-Sludge Wave/Sludge Bomb/Substitute
-Will-o-Wisp
-Taunt
Nature: Timid
EVs: 8 HP/248 SAtk/252 Spe
Item: Black Sludge