Probably something like the following, which still allows for flexibility in terms of movesets if not in Pokemon:
Exeggutor
Gengar
Cloyster
Zapdos
Snorlax
Tyranitar
Egg & Gengar have great synergy together (they converge on very similar Explosion targets) and are very flexible in terms of how they can mess up your day. Both can run Thief, different coverage (HP Fire from Egg, Fire Punch/Dpunch from Gengar) and Sleep moves, Gengar can run Ptrap or Dbond, Egg can do Stun Spore and/or Leech Seed. And they both check enough important things defensively that they don't end up dead weight if you're slightly on your back foot. Gengar's Speed is also super helpful in certain circumstances: outspeeding a DrumZard or +2 Drumlax? Or how about getting the jump on a bothersome Jynx or Tentacruel? Having Speed + Explosion means having flexibility in how you deal with such threats.
Cloyster isn't super flexible but he does have Spikes, which are *that* good. Synergizes well with Gengar's ability to spinblock in a pinch, it converges on Explosion targets with Egg & Gengar, and it *does* have a few tricks up its sleeve (clamp to stop ML + Psong, clamp + screech + explosion to catch Snorlax trying to set up on you, running Ice Beam or HP Electric) to make it unpredictable or even help it wear a hat that the team needs somebody to wear.
Zapdos works well all the time, and even better with Spikes + Explosion support. And it's way more flexible than it's often given credit for. Twave is great, Screens are okay, Whirlwind seems super under-rated (especially with Spikes support), and there's even that weird Sub+Swagger set that honestly seems like it could do some damage - this team does have Explosions to bail it out after all.
Snorlax is ironically probably the least flexible member of this team, because you'll probably want it to be ST to handle Thunders (and just generally be an impenetrable fortress). But it's probably the most flexible Poke in the game set-wise if you take team context out of the equation, and you could still run a "gotcha" set (SelfDestruct? LK? Fire Blast?) to catch opponents napping.
Ttar is way better than Steelix - or at least more fun. YMMV honestly. You lose a Thunder immunity but you get, in return, a Pokemon that actually contributes on offense with Pursuit and coverage. Plus there's opportunities to get creative: Zapdos can be a Phazer, and Gengar/Cloyster can counter-trap to kind-of sort-of fill that role, so you could go with a Screech set or a full-out mixed attacker set. Or you could be boring and run the Phaze + Pursuit set, which still is perfectly fine. Plus it plays backup against Jynx & Sunny Fires whereas Steelix leaves you wide open if Snorlax isn't feeling super well.
