Qorvex. Can be insanely tanky but can also be built for insane clear, can also have good CC, and can have great single target damage with damage amp and armor strip. He can literally do it all.

Further elaborated:

His base armor is the highest in the game, by far. If you want to be extra tanky, toss all 3 umbral mods on, use adaptation, quick thinking, and the arcane that gives you energy based off of armor. Bonus points for rage and health regen. The only thing that can kill you is a rad proceed player or the last tick of a jade eximus beam, because that doesn't seem to do damage, it just kills you outright.

Clear wise, his 4 is absolutely nutty. Every target hit by the beam does an explosion of radiation damage, and that radius scales with ability range, and his 4 has crazy punch through. So, if you fire it into a crowd, every enemy will get hit with the damage a number of times equal to the number of enemies close by. "But that requires enemies being grouped!" I hear you say. Luckily, his 2 does that quite nicely. Additionally, his 1 honestly does pretty high damage, scales great with range, and doesnt require building duration.

Cc wise, his 1 is great, slowing enemies and rad proccing does well for CC, and his 2 is great as well.

Damage wise, he has an augment that lets his 2 armor strip, and makes enemies take more damage.

He's an absolutely terrific frame, 10/10 highly recommend

I think the big limiter here would be excavation maps. Zephyr would be my pick, as long as I can also use some sort of operator mode for spy, but i don't think it's strictly necessary. An un-forma'd Zephyr is steel path capable. ETA: 100% projectile defense for you and the thing you're standing next to is just too good.

Volt, since that's what I did

I don't think there's really a strategy that's necessary. I suppose a high damage single target weapon for shut like demolishers but other than that idk

I've even been able to run my volt on certain Steel Path nodes since the health rework

Ooh thats tough, my initial instinct is Citrine, but I use an Archon build for her that would be a nightmare to get myself to. Probably Mag, Zephyr, or Titania in the end. Titania in particular takes very little to get off the ground and is way less vulnerable to the random toxin proc then Mag is.

If it’s doing the whole thing in one sitting, titania is the obvious choice.

Octavia for sure! Not only is her toolkit good at basically everything, her passive helps with one of the worst early game problems, energy economy. Not being forced to rely entirely on energy drop RNG to be able to maintain your abilities is liberating before Zenurik and other energy generators kick in.

Gauss if obtainable would be a very fun frame to Iron Man. However Sedna is quite late so I don't know if he'd count.

Of the starter Frames, I'd say Mag. Hell, even endgame she's my go-to when shit gets tough.

Ivara, probably. Prowl, sleep arrows, and a good melee or silenced gun can change the world.

Not a popular pick it seems, but I think I'd go with Inaros.

I think the only real requirement for this is that you have some sort of CC/Defense capabilities because higher level defense missions can be rough without a decent frame for them. Interceptions are going to be a pain pretty much no matter what, but they should be doable. Inaros should be able to do both.

My other reason: I like Inaros. I think he's fun.

The only part that would be difficult is getting Rage. Hopefully it'd drop from one of the junction specters, but worst case you can farm Napalms.

An interesting followup question: what weapons do you complete this with? What builds are you using? Do you bother going out of your way to personally farm the rarer mods or just make a decent build with more common stuff?

I'd probably roll Lavos. With a good weapon, Lavydaddy can solo most steel path stuff so I imagine cruising through the star map wouldn't be a major issue.