Oh you select gear, it just gets taken off you.
I hope with the new information this doesn't lead to a hand-drawn Tinder profile!
Ok, joking aside, how about this - the party are the whittled down survivors of a big blag in a sector somewhere where some Inspiring Leader manages to persuade everyone that there's a big treasure, lots of loot, slaves, gear, special crystals that melt on your tongue - whatever.
Unfortunately, the Imperium decides they don't like this very much and beats everyone up. The Lord flees with the goods, leaving you without transport off-world. A dwindling crew of survivors, you get closer over the course of sieges, hit-and-runs, street fighting, and are killed off in batches, with the PC's captured individually over the course of several weeks. The Imperium re-takes the planet and a Lord Inquisitor of the Hereticus pulls strings to get you aboard the prison ship. When you wake up, you know each other from the experience, so there's a little friction, but otherwise, being from different warbands and legions doesn't matter.
You are the Survivors.
Oh Necronaut, the bike thing - I'm tempted to agree to that (should we proceed) but only on the condition that the bike is sentient and vampiric, and you have to power it with your life force, no matter how much fuel you put in it. Either one of your hands or feet MUST be bare so the bike will function.