On the face of it, I think expanding to include Necromunda-ified options from compatible/easily converted makes the most sense.
But - in general - I've always found the "stupid" rules to be, well, stupid. It's a cultural/byproduct thing - clearly - not an innateness. They're human. They've human intelligence, they can do what humans can do, brutalised and maligned or otherwise.
Kits-wise, I expect things like:
- ripper guns (sawn-off heavy stubbers?

)
- bullgryn-y grenade launchers
- knives/butcher blades (Ogryn-y: +1 Damage?)
- ceramite shields
- harpoon launchers (Ogors in AoS have a few)
- stub cannons (actually, most Goliath & Corpse Grinder weaponry makes sense for an overlap, maybe at an increased price/restrictedness to e.g. champions)
- servo claw/hydraulic claw (from the Kataphron Servitors Ad Mech kit - they seem about the right size to bolt-on nicely).
I'd argue a wee skill/rule that let's them "add" sidearm to, I dunno, a basic weapon for a credit cost & int check, maybe with assistance from hangers on (e.g. Weaponsmith, Heretek, Ammo Jack, Brute Handler?), would be pretty swish too. A bit like how Bulging Biceps goes, but a bit more useful, and characterful, you know?
But given that trading post availability is already something most folk feel comfortable with, it's began to play on my mind as: are we better off thinking of what weapons are baseline available to pretty much everyone? And just assuming that - within reason - everyone can likely get their hands on stuff?
Hell, even given gangs a sort of... Credit Rating, based on their house support or something. Basically their starting availability is a generic "Rare" roll value or something, like Cawdor & Goliath only spend XP to buy generic Common availability, Ogryns sit on Common but Illegal 9,Orlocks get Rare8 , Escher Rare 8 & Illegal 8, Delaque Rare 8 & Illegal 10, Van Saar Rare 9 & Illegal 9 etc.
I wouldn't necessarily *balance*, but as a notional "who has easy access to easy things like pole arms" - as you initially note - it does make a degree of sense.
(Also, a clarified/rejigged set of credit values and tweaked rarities/legality, would be quite nice, wouldn't it? Generally, for the game? I know, it's house rules, but it'd be lovely if it was just... Taken As Read, or more conveniently baked into the core system.
Like the Trading Post pdf GW did. Would shake things up and make it all a bit easier for folk to get their teeth into.
[Though, in fairness, that's been done a touch in the new rulebook - think they could just be more proactive in it. Do it like the 40k meta tweaks, but call it, I dunno, "Market Fluctuations", or "The Really Blatant Hand of the Imperial House", proper economics like.])